Singh made his screen debut with a small role in
Raanjhanaa (2013). He expanded into films with brief roles in the 2015 films
Aligarh and
Tamasha and had a bigger role in the romantic drama
Tum Bin II (2016). He then played a supporting role opposite
Sonam Kapoor in the comedy
Veere Di Wedding (2018). In 2019, he had a small role in
Sanjay Leela Bhansali-produced film
Malaal, starring
Sharmin Segal and
Meezaan Jafri. In 2020, Singh starred as Imran Ansari, a young, idealistic cop in the
Amazon Prime Video crime thriller series
Paatal Lok. Reviewing the series for
The Indian Express, Shubhra Gupta labelled him as "impressive". Priyanka Roy of
The Telegraph considered him to be "the find of the series". He was nominated for a
Filmfare OTT Awards, for Best Supporting Actor in a Drama Series. Singh next played a supporting role in one segment of the
Amazon Prime Video anthology film
Unpaused (2020). In 2022 and 2023, he portrayed
Vikram Sarabhai opposite
Jim Sarbh's
Homi J. Bhabha in the
Sony LIV drama series
Rocket Boys. Journalist Anuj Kumar of
The Hindu opined, "As the genteel but determined Sarabhai, Ishwak Singh proves to be an effective foil to Sarbh. His honest smile wins half of the battle in essaying a complex role." He also starred in the horror series
Adhura and the second season of the drama series
Made in Heaven, both for Amazon Prime Video. Also in 2023, Singh starred in the spy thriller film titled
Berlin, alongside
Aparshakti Khurana, and
Tumse Na Ho Payega alongside
Mahima Makwana. The former film premiered at the
Indian Film Festival of Los Angeles in 2023 and was released on
ZEE5 the following year. The critic
Saibal Chatterjee labelled Singh's performance as a deaf-mute man accused of being a foreign spy as "at once expressive and mystifying". In 2025, Singh reprised his role as Ansari in the second season of
Paatal Lok. ==In the media ==