According to IANS, the Cloud Atlas star had read about Khan in the September issue of TIME magazine, in which the Satyamev Jayete star was described as "India's first superstar activist".
Hanks is reported as saying in a statement: "I really admire the work that Aamir Khan is doing (in India). Very few celebrities take the initiative of coming forward to change the society and he has done a remarkable job.
"It's the 'giving-back' that's tough. Aamir seems to understand the influencing power of being a celebrity and is using it to act as a catalyst for change in society, something that definitely deserves both appreciation and support from all quarters."
Khan has raised public awareness of social issues such as female foeticide, domestic violence and medical malpractice on his popular TV show Satyamev Jayate.
Aamir Khan is the first non-MP Bollywood actor to be invited to the Indian Parliament and the third Bollywood actor to appear on the cover of TIME.
The 3 Idiots star has been widely praised for his debut TV show on Star Plus.
Starring Halle Berry and Hugh Grant, Cloud Atlas releases in the US and India on October 26, and in the UK on February 22, 2013. Watch a trailer for the film below: