Westheimer was born Karola Ruth Siegel on June 4, 1928, in Wiesenfeld (now part of Karlstadt am Main), Germany, the only child of Orthodox Jews, Irma (née Hanauer), a housekeeper, and Julius Siegel, a notions wholesaler and son of the family for whom Irma worked. She was given an early grounding in Judaism by her father, who took her regularly to the synagogue in the Nordend district of Frankfurt, where they lived. Her father was taken away by the Nazis a week after Kristallnacht, or the Night of Broken Glass, in 1938. Westheimer cried while her father was taken away by men in gloss-finished boots, while her grandmother gave the men money and asked them to care for him. Westheimer’s mother and grandmother decided that Germany was too dangerous due to the tension and Nazi violence growing, so in January 1939 they sent Westheimer on the Kindertransport to Switzerland. Westheimer, age 11, arrived at an orphanage of a Jewish charity in Heiden and took on the role of a caregiver and mother-like figure to the younger children there. Westheimer was not allowed to take classes at the local school, but a fellow orphan boy would sneak his textbooks to Westheimer at night so she could learn and continue her education.

While at the orphanage, Westheimer corresponded with her mother and grandmother via letters. When the letters ceased in 1941, Westheimer knew she would not hear from them again. The details of her parents’ deaths due to the Holocaust are also included in the Hulu documentary about Westheimer titled Ask Dr. Ruth. Her father was killed in the Auschwitz concentration camp in 1942. Her mother was killed during the Holocaust, but there is no specific information about her death, or about how and when she died. In the data base at the Yad Vashem World Holocaust Remembrance Center, Westheimer’s mother is categorized by the word verschollen or ‘disappeared.’

Westheimer decided to emigrate to British-controlled Mandatory Palestine. There, at 17, she “first had sexual intercourse on a starry night, in a haystack, without contraception.” She later told The New York Times that “I am not happy about that, but I know much better now and so does everyone who listens to my radio program.” Westheimer joined the Haganah in Jerusalem. Because of her diminutive height of 4 ft 7 in (1.40 m), she was trained as a scout and sniper. Of this experience, she said, “I never killed anybody, but I know how to throw hand grenades and shoot.” In 1948, Westheimer was seriously wounded in action by an exploding shell during the 1947–1949 Palestine war, and it was several months before she was able to walk again.

In 1950, Westheimer moved to France, where she studied and then taught psychology at the University of Paris. In 1956, she immigrated to the United States, settling in Washington Heights, Manhattan. Westheimer earned an M.A. degree in sociology from The New School in 1959 and an Ed.D. degree from Teachers College, Columbia University in 1970.

Westheimer became a naturalized U.S. citizen in 1965. She regained her German citizenship in 2007 through the German Citizenship Project that enabled descendants of Germans deprived of their citizenship during the Third Reich to reclaim their citizenship without losing the citizenship of their home country.

Dr. Ruth’s media career began in 1980 when her radio show, Sexually Speaking, debuted on WYNY-FM in New York City. She was offered this opportunity after she gave a lecture to New York broadcasters about the need for sex education programming to help deal with issues of contraception and unwanted pregnancies. Betty Elam, the community affairs manager at WYNY, was impressed with her talk and offered Westheimer $25 per week to make Sexually Speaking, which started as a 15-minute show airing every Sunday at midnight. By 1983 her show was the top-rated radio show in the area, and in 1984 NBC Radio began syndicating it nationwide as the Dr. Ruth Show. She went on to produce her radio show until 1990. Described as the “Sister Wendy of Sexuality”, Dr. Ruth helped to revolutionize talk about sex and sexuality on radio and television, and she was noted for having “an accent only a psychologist could love”. She became known for being candid and funny, but respectful, and for her tag phrase “Get some”. One journalist described her unique voice as “a cross between Henry Kissinger and Minnie Mouse”.

In 1984, Westheimer began hosting several television programs on the Lifetime TV network and one in syndication. Her first show was Good Sex! With Dr. Ruth Westheimer, airing for a half hour at 10 pm on weeknights. This show was expanded in 1985 to a full hour and its name was changed to The Dr. Ruth Show. In 1987 she began a separate half hour syndicated series on many broadcast stations called Ask Dr. Ruth which was co-hosted by Larry Angelo. Dr. Ruth returned to the Lifetime network in 1988 with The All New Dr. Ruth Show, which was followed in 1989 by two teen advice shows called What’s Up, Dr. Ruth? and a call-in show, You’re on the Air with Dr. Ruth in 1990. In 1993 Westheimer and Israeli TV host, Arad Nir, hosted a talk show in Hebrew titled Min Tochnit, on the newly opened Israeli Channel 2. The show was similar to her US Sexually Speaking show. The name of the show, Min Tochnit, is a play on words: literally “Kind of a program”, but “Min” (מין) in Hebrew also means “sex” and “gender”.

Westheimer has been married three times. She said that each of her marriages played an important role in her relationship advice, but after two divorces, it was her third marriage, to Manfred ‘Fred’ Westheimer, that was the “real marriage”. She met Fred on a skiing trip in the Catskills. Fred, too, had escaped Nazi Germany. Their marriage lasted until his death in 1997. She has two children, Miriam and Joel, and four grandchildren. In December 2014, Westheimer was a guest at an Orthodox Jewish wedding in the Bronx. The groom, Rabbi Benjamin Goldschmidt, is the great-grandson of the woman who had helped rescue Westheimer from Nazi Germany. She still lives in the “cluttered three-bedroom apartment in Washington Heights where she raised her two children and became famous, in that order,” to be near the two synagogues of which she is a member, the YMHA of which she was president for three years, and a “still sizable community of German Jewish World War II refugees.” She speaks English, German, French, and Hebrew.

Between 2001 and 2007, Westheimer made regular appearances on the PBS children’s television series Between the Lions as “Dr. Ruth Wordheimer” in a spoof of her therapist role in which she helps anxious readers and spellers overcome their fear of long words. In January 2009, the 55th anniversary issue of Playboy magazine included Westheimer as #13 in a list of the 55 most important people in sex from the past 55 years. In October 2013 the play Becoming Dr. Ruth opened Off Broadway. Actress Debra Jo Rupp played the role of Dr. Ruth. The play showcased the sex therapist’s life from fleeing the Nazis in the Kindertransport and joining the Haganah in Jerusalem as a scout and sniper, to her struggles to succeed as a single mother coming to America. Eileen DeSandre played Dr. Ruth in the Virginia Repertory Theatre production of Becoming Dr. Ruth.

Westheimer has delivered commencement speeches at the Hebrew Union College seminary, Lehman College of the City University of New York and, in 2004, at Trinity College, where she has been awarded honorary degrees. She also taught courses and seminars at Princeton and Yale, and was the guest speaker at the Bronx High School of Science in New York in commemoration of Yom HaShoah 2008. Westheimer spoke about her life story and the audience of 500 sang “Happy Birthday” in honor of her 80th birthday. At the ceremony she received an honorary Bronx High School of Science diploma. In 2002, she received the Leo Baeck Medal for her humanitarian work promoting tolerance and social justice.

In the 1980s and 1990s, Westheimer was a frequent guest on late-night talk shows like The Tonight Show and Late Night with Conan O’Brien. She also appeared on talk shows on German television. In 2019, she was a guest on The View, The Today Show and Late Night with Seth Meyers.

A documentary about her life, Ask Dr. Ruth, premiered in U.S. theaters on May 3, 2019 and was released on Hulu on June 1, 2019.

Westheimer continues to be an active figure. In addition to the documentary released about her this year, she has recently published her 45th book. On her 91st birthday (June 4), Westheimer visited the Ellen DeGeneres show, and visited Ellen’s show again in November 2019, taking questions from the audience. In 2019 alone, Westheimer has appeared on Late Night with Seth Meyers, The View, and Strahan, Sara and Keke.