Shashwat started his career in 2011 in Hollywood, Los Angeles working on numerous projects before moving to India in 2016. In 2017, he was chosen as the music composer for Phillauri, which starred Anushka Sharma and Diljit Dosanjh. In 2018, he composed four songs for Veere Di Wedding, a Bollywood female buddy comedy film, directed by Shashanka Ghosh. The film starred Kareena Kapoor Khan, Sonam Kapoor Ahuja, Swara Bhaskar and Shikha Talsania. In the same year, he scored for Selection Day, an Indian Netflix Original sports web television series, based on Aravind Adiga's 2016 novel of the same name. It was produced by Anil Kapoor and Anand Tucker. In 2019, he composed the music as well as the background score for Uri: The Surgical Strike, an Indian action film written and directed by debutant Aditya Dhar, and produced by Ronnie Screwvala under his banner RSVP Movies. The film, starring Vicky Kaushal, is based on the 2016 Indian Army's surgical strikes on PoK in retaliation for the Uri attack. The film's music received rave reviews. His background score was also appreciated and released separately on popular demand. Shashwat won the award for Best Background Music at the 66th National Film Awards and the IIFA Award for Best Background Score at the 21st IIFA Awards for Uri: The Surgical Strike. He also won the 65th Filmfare R.D. Burman Award for Best New and Upcoming Talent. In 2021, he released a production album titled Euphoria (And the Following Realities) under Extreme Music. The track "Dharma", from the album, won Best World Production Music 2021 and Shashwat himself won PRS Foundation The Best Newcomer 2021 in the Production Music Awards 2021 held in London on 12 December 2021. In 2022, he worked on the soundtrack of the film Attack, an Indian Hindi-language superhero film directed and co-written by Lakshya Raj Anand. The film produced by Jayantilal Gada, John Abraham and Ajay Kapoor, starred John Abraham alongside Jacqueline Fernandez and Rakul Preet Singh. Shashwat, released independent music with a new label called IndieA Records launched in India with the intention to nurture and promote independent artists backed by Universal Music India. He dropped his first piece of music with them called "Awaara Ho". 2024 saw his work on the soundtrack for the film Article 370, a political action thriller film directed by Aditya Suhas Jambhale, who co-wrote the film with Aditya Dhar, Arjun Dhawan, and Monal Thaakar. Produced by Jyoti Deshpande, Aditya Dhar, and Lokesh Dhar, the film stars Yami Gautam, Priyamani, Skand Thakur, Ashwini Kaul, Vaibhav Tatwawadi, Arun Govil, and Kiran Karmarkar in pivotal roles. Shashwat worked as a featured artist on Hans Zimmer and James Everingham's score for the 2025 BBC crime thriller Virdee, based on AA Dhand's much-loved novels. The six-part series was adapted for the screen by AA Dhand and was produced by Magical Society for BBC One and BBC iPlayer. In August 2025, he composed the soundtrack for web series The Ba***ds of Bollywood. In December 2025, he worked on the soundtrack of the film Dhurandhar. His second collaboration with Aditya Dhar, after Uri: The Surgical Strike, it received widespread acclaim, with its modern reinterpretations of nostalgic source material, and contributions from Hanumankind, Reble, Diljit Dosanjh, Simran Choudhary, Arijit Singh and Jasmine Sandlas among others, being highlighted as the main reason for its success.India Today praised the creative reworking of retro melodies, calling the result "fresh, exciting, and tightly woven" into the film's contemporary action drama, resonating with audiences across generations. He is now set to compose the soundtrack for Dhurandhar: The Revenge and the Ram Charan-starrer India House.