Sinha started her career as a costume designer, designing the costumes for films like Mera Dil Leke Dekho in 2005 , and walked the ramp at the Lakme Fashion Week 2008 and then again in Lakme Fashion Week 2009.
She made her acting debut in the 2010 film Dabangg, in which she starred opposite Salman Khan. The film went on to become the highest grossing film of 2010, and ultimately emerged as an all-time blockbuster. Sinha had to lose 30 kg in preparation for the role as a village girl. Her performance was well received, with noted critic Taran Adarsh noting that "Sonakshi Sinha looks fresh, acts confidently and pairs off very well with Salman. Most importantly, she delivers the right expressions and is not overpowered by the galaxy of stars in the cast."
Sinha is a professed animal lover, and she had posed for a PETA campaign advocating the adoption and sterilization of dogs and cats.