Margarita with a Straw premiered worldwide at the 2014 Toronto International Film Festival, where it received a standing ovation. The event was attended by the cast and crew, including Bose and Koechlin; the latter said that she was overwhelmed by the response and "loved to see the audiences cry and laugh with the movie". The film was subsequently screened at film festivals across Europe, including the Tallinn Black Nights Film Festival, the BFI London Film Festival, the Galway Film Fleadh, the Vesoul Festival of Asian Cinema, and the Giffoni International Film Festival. Margarita with a Straw had its American premiere at the 2015 Palm Springs International Film Festival. It was screened in Castro Theater at CAAMFest, and shown at the Santa Barbara International Film Festival later that year. The film opened the 2015 New York Indian Film Festival, and also featured at the 19th Busan International Film Festival and the Istanbul Film Festival. Out on Film, Miami Gay & Lesbian Film Festival, and Reeling were among the LGBT events that screened the production.
After garnering acclaim at the international film festival circuit, the producers of Margarita with a Straw sent it straight to the Central Board of Film Certification. The decision to not send it to any of the major Indian film festivals was looked upon by commentators such as Uma Da Cunha, editor for Film India Worldwide, as a part of a marketing strategy. Srinivasan Narayan, organiser of the Mumbai International Film Festival said that while Indian film festivals have grown, they have not yet reached a level where they can compete for international premieres. Instead, Margarita with a Straw had pre-released screenings for members of the Indian film industry in Mumbai. Along with the cast and crew of the production, these showings were variously attended by Amitabh and Jaya Bachchan, Aamir Khan, Kiran Rao, Vidya Balan, Anurag Kashyap, and Shraddha Kapoor. The film was positively received at the time; Bollywood personalities including Khan and Hrithik Roshan hosted separate special screenings for the film.
Ahead of its commercial release, the crew organised several promotional events. In an interview with the Indo-Asian News Service, Koechlin talked about the importance of marketing for an independent film, saying that although the content of the films is becoming better, Bollywood remains an industry largely driven by box office gains. Bose wanted the film to be marketed as a commercial one despite its art house appeal; she was not very keen on sending it to film festivals and later asked the producers to avoid mentioning the accolades that the film had won at any of the promotional events. The official trailer was released on 4 March 2015 on Viacom 18 Motion Pictures' official YouTube channel. First look posters featuring Koechlin sipping margaritas using a drinking straw were also unveiled on the same day. The film was released theatrically in India on 17 April 2015.