Nicolaescu’s debut as a director was in 1962 with the short film Scoicile nu au vorbit niciodată (Shells Have Never Spoken). His first feature film was the 1967 French-Romanian co-production Dacii (Les Guerriers). The film was entered into the 5th Moscow International Film Festival. Nicolaescu continued his film-making career by both directing a large number of movies and starring in many of his own films. His 1971 film Mihai Viteazul was entered into the 7th Moscow International Film Festival. As an anecdotal detail, in Steven Spielberg’s E.T. The Extraterrestrial (original version only), the young boy Elliott watches this movie on TV – Mihai Viteazul in the US version – the scene with the battle of Calugareni. His 1976 film The Doom was entered into the 10th Moscow International Film Festival.

His movie Mihai Viteazul was considered the best of the Romanian historical movies and is one of the most appreciated world-wide of this kind (for example, considering imdb ratings) . The film was released in 1970 in Romania, and worldwide by Columbia Pictures as The Last Crusade. A TV sequence in Steven Spielberg’s “E.T.” (original, uncut version) show images from “Mihai Viteazul” (scenes with the Battle of Călugăreni).

His 1985 film The Ring was entered into the 14th Moscow International Film Festival. For this movie, Nicolaescu performed a very intensive boxing training with a former European boxing champion. The intensity of his training for this movie was similar to what the Romania’s Olympic boxing team at that moment performed. At that time Nicolaescu was 50 years old and its boxing matches and the hits during this movie are real and against strong opponents.

Nicolaescu started his political career during the 1989 Romanian Revolution. At the time the Revolution took place he was very well known and respected for his films, in Romania. He participated actively at the Romanian Revolution and his appearance and speech during the Revolution brought about coherence and clarity to the people who listened. In December 1989 he was received with a standing ovation (his name) from the crowd of hundreds of thousands of Romanians gathered in the heart of Bucharest after Nicolae Ceaușescu left power on 22 December 1989. He called for calm, and asked the crowd to listen to and support Ion Iliescu. Nicolaescu went on to play an important political role during the Revolution and was elected to the Romanian Senate in 1992 as a member of the Romanian Social Democratic Party. He left the party in April 2011, and then rejoined it after only two days.

In 2005 Nicolaescu declared in an interview that he was not happy with his decision of going into politics. He felt that the politics took too much from his precious time and because of that he was not able to do as many films as before the Revolution.

Nicolaescu had been diagnosed since 2000 with diverticulitis, a benign and chronic digestive condition that was acting up every couple of years. In January 2008 he underwent brain surgery twice due to an accident. At that time, he was 78 years old. The doctors did not give him any chance for success because at the time of his first brain operation he was completely paralyzed. He had to learn how to walk, speak and write again, and he successfully managed to do it after 3 months of intense physiotherapy and neurological exercise. Nevertheless after this brain surgeries he said he changed dramatically: he started feeling his age and he started changing his behaviour (more impatient and irritable). In his last years the health problems made his life difficult. Yet he continued directing, acting and planning new films. He maintained intact his huge passion for filmmaking until the end of his life.

Although he was never a very passionate football fan, Nicolaescu stated in a 2011 interview for the Romanian daily sports newspaper Gazeta Sporturilor that capital-based team Steaua București was the dearest to him throughout time, even though he played rugby at Dinamo București. He explained this by saying that he liked the former Steaua legends Gheorghe Hagi, László Bölöni and Dan Petrescu more than Dinamo’s players. Nicolaescu declared in the same interview that he also liked Ripensia Timișoara and Universitatea Craiova in their glory days, but not as much as Steaua.

On 26 December 2012 he was admitted with atrial fibrillation and a traumatised thorax with pulmonary contusion to the Elias Hospital in Bucharest. He complained of pain in the lower abdomen and loss of appetite. After the clinical examination, the doctors concluded that he was suffering from an acute episode of diverticulitis, and he received treatment for this condition. During the treatment, Nicolaescu’s condition improved, but the intestinal transit was not functional and the blood work was still unsatisfactory. The doctors opted for an exploratory laparoscopy, which led to the discovery of an acute perforated appendicitis complicated with peritonitis. After undergoing surgery, Nicolaescu developed respiratory complications, leading to acute respiratory failure within 48 hours. He entered into cardiac arrest on 3 January 2013, and could not be resuscitated by the hospital staff. He was pronounced dead at 8:20 AM GMT+2. His body was cremated on 5 January 2013, according to his wishes.