Tendulkar said he accepted an offer from the Indian Olympic Association (IOA) to work alongside Khan, whose appointment triggered a row over whether an actor was best suited to promote sports among people.
Sachin Tendulkar bats for campaign against child labour on Twitter
"I have had the privilege and honour of representing our nation for 25 years and I continue to bat for India off the field," the master batsman wrote in a letter to IOA chiefs.
"The welfare of sportspersons and encouraging them to give their best is dear to me."
The IOA named more ambassadors, including ace Indian shooter Abhinav Bindra and Oscar-winning musician AR Rahman, in the days after the controversy over Khan.
Olympic wrestler Yogeshwar Dutt had criticised Khan's appointment, saying the "Olympics is not a place to promote films". Indian sprint legend Milkha Singh had urged the government to intervene to overturn the decision.
Twitter reacts as Salman becomes India's ambassador for Rio Olympics
However, the IOA has defended its decision. It says the 50-year-old actor is popular among young people.
Tendulkar, who is widely revered in cricket-mad India, played 200 Tests and 463 one-day internationals, knocking up a record 100 centuries in both formats, before retiring in 2013.
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ