She was born in Chennai into a Roman Catholic family to Anthony Devraj and Regina Mary Nirmala. Her ancestors were from Paramakudi near Madurai. Since there was already another established singer with the name of M.S.Rajeshwari her name was abbreviated into L.R.Eshwari. She did not have any formal training in singing. Her mother was a chorus singer in films. Her first break came from Thiru. K.V.Mahadevan in 1958 in the movie 'Nalla Idaththu Sammandham', her first solo song recorded in this movie was 'ivarey thaan avarey'. Her unique voice was considered to be suited for peppy numbers in the movies, be it a dance tune, folk song or a devotional track. Her song "Vaarayo Thozhi" from Paasa Malar was a popular choice for wedding music. Her "Chellatha" and "Karpoora Nayagi" numbers has won her a lot of fame among devotees. She sang Christmas songs "Varuvai Varuvai" and " Deivam thantha divya kumaaran" composed by Dr Anand Chellappa. Perhaps she and P.Susheela were the most popular female-duet-duo ever, they complimented each other perfectly in terms of voice and style, and sang very many popular duets in their times – unadhu malar, chiththira poovizhi, ninaithaal sirippu, thoodhu sella etc..
After a long break, she made her re-entry through a rocky peppy Tamil Song "Kalasala Kalasala " in the 2011 movie Osthe starring Silambarasan. Within a few days of this song release, it became a super hit and reached music box office top ratings. She sang the song "Naa Poondamallida" in the film Thadaiyara Thaakka the following year.