Saikumar is the only son of the yesteryear actor Kottarakka Sreedharan Nair and Vijayalakshmi Amma. He has seven sisters, five elder and two younger. He was first married to Prasanna Kumari, but their marriage collapsed when Saikumar came to know that Prasanna Kumari was six years older than him. They have a daughter named Vaishnavi from this marriage. He later married actress Bindu Panicker in 2009.
Saikumar started his career in cinema as a child artist in Vidarunna Mottukal. He started his career in theatres. He was offered the lead role in the film Swathi Thirunal, but it was later done by Anant Nag. He made his debut in the blockbuster Ramji Rao Speaking (1989). It was directed by two debutantes, Siddique and Lal (Siddique-Lal), and had debutant actors Saikumar and Rekha in the lead. Saikumar debuted in the 1977 film Vidarunna Mottukal as child artist. He started his career with comedy roles, and gradually moved to character roles. He won Kerala State Film Award for Second Best Actor for his performance in the 2007 film Anandabhairavi.
The success of the film helped him to earn a lot of opportunities in the next few years. He has done leading roles in a few films like Sauhradam, Thudarkkatha, Khoshayathra, Anantha Vrithantham, Thooval Sparsam, etc. But in that age of comedy, he could not make an impact as a hero while Mukesh, Jagadeesh and Siddique were cast in the small budget movies. Saikumar remained active in the industry with supporting, character and negative roles in films including In Harihar Nagar, Saandram, Makkal Mahalmyam, Griha Pravesam, Ayushkalam. The sequel to Ramji Rao Speaking, Mannar Mathai Speaking was a blockbuster of 1995. This time Mukesh played the lead role. His villain roles in Mammootty's 1996 blockbuster Hitler was noted. This earned him the reputation of acting the intelligent villain. Saikumar's real talent was shown once again in the year 2004 in the film Sethuramayyar CBI. He wisely recreated the sound modulation and mannerisms of the late actor 'Sukumaran, ' as because the character which Saikumar had done was the son of Inspector Devadas in the film Oru CBI Diary Kurippu .
Saikumar's golden period started in the late 1990s. He was cast in the super hit Aaraam Thampuran by Shaji Kailas where he played the close friend of hero acted by the Malayalam film star Mohanlal. Then he became the inevitable ingredient of all the superstar movies. He played villain to Mohanlal in Narasimham (2000), Thandavam (2001), and Chathurangam (2001). His prominence was evident from the posters of Thandavam where his pictures were printed the same size as Mohanlal's. In movies like Valliettan and Vesham he played villain to Mammootty. In the Dileep movie Kunjikkoonan (2002), he appeared in a completely different get-up of a cruel Goonda, which was much acclaimed.
2005 was a very good year for Saikumar in which he acted in Rajamanikyam, Mammootty's mega-hit where he played an elder man. This made the directors rethink his range of characters. In Suresh Gopi's comeback film Bharathchandran I.P.S., he played the villain. He described the role as an anti-hero not a villain, since he leads story in the first 45 minutes until Suresh Gopi appears. He also played the supporting role as DYSP Pothen in the Suresh Gopi hit The Tiger.
He lent his voice for Sathyaraj in Aagathan & also dubbed for Thiagarajan in Thilakkam.
In 2007, he won accolades for his performance as a Kathakali artist and the father of a highly talented but ailing son in Anandabhairavi. Director Vinayan described him as talented as Mohanlal which is the best compliment for his acting abilities.
2007 - Kerala State Film Award for Second Best Actor for Anandabhairavi
2006 — Asianet Film Awards for Best Character Actor Award for Chakkara Muthu
2015 - Asianet Film Award for Best Supporting Actor for Ennu Ninte Moideen