Al Sahir was born in Mosul, Iraq on September 12, 1957. His father lived in Baghdad, but was a Samarra native from the tribe of Darraj his mother from Najaf. He grew up and spent a large part of his life in Al-Hurrya neighborhood in Baghdad. He is the son of a palace worker and has nine siblings.

He excelled in his studies and entered the Teachers Institute where he graduated in 1978 and was appointed as a teacher in a school in Mosul. He taught Music lesson in Mosul, Aqrah region where he was introduced to the beautiful nature of Northern Iraq. His interest in music grew as he listened to songs via the radio that offered him the chance to become familiar with the works of composers such as Mohammed Abdel Wahab.

One of his first videos was made in collaboration with one of his friends that happened to be a television director. The song in question was “Ladghat El Hayya” (The Snake Bite), which was broadcast on Iraqi television in 1987, one year before the end of the Iran–Iraq War. The song was the source of a major controversy due to particular sensitivities that were common during that era. Iraqi television officials asked him to either change the lyrics or have it banned. His refusal to change the lyrics and its consequent ban only helped to increase the popularity of the song. He began giving concerts all over the Persian Gulf and recording his music with Kuwaiti labels.

A year later, he had a hit with “Obart Al Shat” (I crossed the river). Some of his professors at the Academy denounced it as sha’bi (pop) music, anathema to those who taught classical music. Al Sahir had managed to circumvent the system and had become a star on his own terms—he even undertook his first US tour in 1989. Having conquered pop, Al Sahir turned around and established himself in the Arabic classical world with “La Ya Sadiki” (No, My Friend), a magnum opus that lasted almost an hour and found him using maqams (scales) that hadn’t been used in Iraqi music in several decades, revitalizing a tradition.

In 1991 and due to the Persian Gulf War, Al Sahir transferred his base of operations to Jordan where he lived with his family for a few years. He considers living in Jordan as an important period of his life and career success later on. Al Sahir performed some of his most successful concerts which were held in Jerash and produced two successful albums at Sameer Baghdadi’s Studios in Amman, Jordan.

After that he moved to Lebanon, where he met and formed a songwriting partnership with Syrian poet Nizar Qabbani in 1996, who wrote lyrics to his music, before settling permanently in Cairo. Nizar Qabbani, who previously wrote lyrics to 1960s-1970s super-stars like Abdel Halim Hafez and Najat Al Saghira, wrote the lyrics to more than 30 of Al Sahir’s songs. In addition to Qabbani’s poems, Al Sahir sang both political and romantic songs for Iraq and Baghdad, highlighting the feelings of the citizens of Iraq as well as their tragedies.

By 1998, he had ten albums under his belt and was lauded as an artist, not just a pop star. That prestige brought him wider fame and a growing international reputation that won him a UNICEF award for his song “Tathakkar”, which he performed in the U.S. for Congress and the United Nations – one of the first real post-Gulf War cultural exchanges. The following year, he recorded a tribute to the Pope with the Italian Symphony Orchestra.

In 2004, Al Sahir collaborated with Lenny Kravitz and released an anti-war song at Rock The Vote, titled “We Want Peace”, and shortly afterward released a song entitled “The War Is Over” (Entahat al harab) with Sarah Brightman, which was released on her album Harem and his album Hafiat Al-Kadamain which was highly praised in the middle east. Both of these international duets were executive produced by Dergham Owainati, of EMI Music Arabia, for Kadim’s part.

In 2004, Al Sahir continued to work with various international artists including Grammy Award-winning producers KC Porter, and Quincy Jones. His collaboration “Love & Compassion” (Hob Wa Haneen) was the title track for the Arab American National Museum Collector’s edition honoring the artists that have made the most significant difference with international audiences. The track features Grammy winning singer/songwriter Paula Cole, Def Jam recording artist Karina Pasian, and Luis Conte, produced by KC Porter and Dawn Elder.

In 2004, he participated in the worldwide broadcast concert special “We are the Future” concert produced by Quincy Jones and coordinated by Dawn Elder at the Roman Maximos Stadium in Rome for the benefit of the children of the world. In December 2004 he participated in the opening of the Gulf Football Championship (Khaleeji 17) in which he performed the return of Iraq Operette which was broadcast live on 10 satellite channels. Additionally, in 2004 he was the first Arab artist to participate in Unity, the official album of the 2004 Summer Olympics.

Releasing his album Ila Tilmitha on November 11, 2004. The album contains collaborations with the Moroccan Asma Lmnawar whom Kadim Al Sahir discovered earlier and introduced to the Arab world in her first due song with Kadim “ashko ayaman”. The album also included the song “Ahbeni” written by poet Nizar Qabbani, shoot as a video clip by Husien Duibes and it was a major hit in the year 2004 alongside the song “Ila Tilmitha”

He sang Bokra “Tomorrow”, a charity single that was released on November 11, 2011 at 11:11 pm, along with Rim Banna, Akon, Tamer Hosni, Diana Karazon, Marwan Khoury, Latifa, Souad Massi, Hani Mitwassi, Saber El Robai, Wa’ed, Sherine and other Arab artists. The single will distribute the proceeds of its donations to various organisations, institutions and charities with arts and culture programs. The eight-minute song was written by Majida Al-Roumi, and produced by Quincy Jones and RedOne.

He is debuted as a coach for MBC The Voice Kids and his team member Lynn Hayek from Lebanon was the winning contestant in the Season 1 Finale held on March 5, 2016.

In February 2019, Kadim officially asked to change his last name from Al Samarai to Al Sahir.