Rajendar started off in the Kollywood industry making successful films which included him as an actor, playback singer, dancer and scriptwriter. He gained popularity through his one-of-a-kind style of acting. He normally serves as, but not limited to director, actor, songwriter, art director, production manager and playback singer. During the 1980s, all his movies were blockbusters, running for years and the songs were also well appreciated. He is known for introducing new faces in his movies, and many of the actresses who debuted in his movies have been successful in South Cinema, including Amala, Nalini, Jyothi, Jeevitha, and Mumtaj.
After some years, Rajendar's films started to decline in popularity because his films became too predictable, tending to follow the same storyline and oratory style of repetitious dialogues with little if any meaning. For example, his films always contain a sentimental scene involving the hero's younger sister in distress, coupled with the same rhyming rhetoric and gestures.
Rajendar recently started his own web TV channel called 'Kural TV' (Voice TV). Originally he wanted to start a 24-hour TV channel but could not, due to problems arising while securing a license. The channel, apart from broadcasting his movies and speeches, tends to echo sentiments towards the plight of Tamils (especially women) in Sri Lanka.
Rajendar had started talking with "common" people through Skype and discussing latest politics in the recent years. Rajendar also distributes films under his home banner "Simbu cine arts". His latest film distribution, as of mid-2011 is his son Silambarasan's film Vaanam, which will be distributed in the Chennai and Madurai region.
Since early 2008, Rajendar has been slowly working on the production of a film titled Oru Thalai Kadhal, a tale based on a village singer, in which he stars in the lead role. In 2011, he released a first look poster for the film and revealed that three heroines from Mumbai would star alongside him. He provided an update in 2014, that the film was still under production and that it was sixty-five percent complete. He has also revealed that he was working on a script to launch his second son, Kuralarasan, as a lead actor.