Alka was born to M.P. Ajith Kumar and K. Sajitha. Her paternal grandfather was a noted singer. Her father Ajith Kumar is a professional musician and organist, who runs Alka's orchestra, "Sangeeth Sagar". Alka first learnt music from her father.
Alka gave her first public performance when she was two and half years old in 2000, where she sang the Hindi language song, "Soldier ... ... Soldier... ". In 2001, she won International UNESCO Club of Repalle (A.P) award and Gold Medal, and in 2002, she won the Rotary International achievement award and gold medal.
When she was four years old, she cut her first audio album, "I love my India". In 2003, Alka entered the Limca Book of World Records, and won the title Bharatheeya Gourav Puraskar in New Delhi. In 2003, she won the Sauparnika Theeram Mini Screen Award, and Thalassery Drishya Kala's A. T. Ummer Award.
Before reaching the age of seven, Alka has sung more than 5,000 songs, could sing in 11 languages, and has given more than 500 concerts across India.
In 2010, Alka shot to fame after becoming a finalist of Airtel Super Singer Junior (season 2), a Tamil language music competition reality TV show broadcast on Vijay TV. She regularly participated in the competition since 2009, and was crowned the winner of the competition.
She subsequently made appearances on Airtel Super Singer 3, and Airtel Super Singer Junior 4 as a guest performer.
Alka made her debut as a playback singer with the song, "Chirakengu" in the Malayalam language movie The Train starring Mammootty after being spotted by Srinivas during the grand finale of Airtel Super Singer Junior (season 2).
In 2008, her debut music album Chakkaramuthu was released, consisting of songs she sang at the age of 10.