Koechlin appeared alongside Parineeti Chopra, Richa Chadda, and Bhumi Pednekar in Y-Films's mini web-series Man's World, a satire on gender roles. The series was released on YouTube in April 2015. She then starred in Anu Menon's Waiting, an independent film about the relationship between two people who befriend each other in a hospital, while nursing their respective comatose spouses. Koechlin played the role of Tara Deshpande, a young and brash social media-savvy. She dyed her hair black for the role, as Menon wanted her to look more "earthy". The film had its world premiere at the Dubai International Film Festival (DIFF) in December 2015, and had its theatrical release in India on 27 May 2016. The film and her performance received positive critical reviews. Sukanya Verma of Rediff.com called the film "absolutely riveting", and also lauded the "stunningly unhindered" Koechlin writing that she used her aura, "in the most mesmeric fashion to create a woman we sympathise with and wish well for". Film critic Kunal Guha thought that film belonged to Koechlin who, "impresses by managing to wordlessly convey her character's state of mind in every scene".
Koechlin advocates for the LGBT rights, and has featured in such video campaigns as Jagatjit Industries's IICE Vodka advertisement "Kinki Chilli". Directed by Shiven Surendranath, the video emphasised on an individual's freedom to choose their sexual identity. Koechlin expressed her support to LGBT community in an International Women's Day interview with The Huffington Post saying that education was essential for developing sensitisation to LGBT rights. Video messages recorded by Koechlin and Kunal Kapoor, in which they voiced their support for the LGTBQ community were screened at the 2016 Delhi International Queer Theater and Film Festival. Koechlin was featured on the March 2015 cover of Bombay Dost, India's first gay magazine.
Koechlin is also vociferous on a variety of other issues, including health promotion, education for children in rural areas, and child sexual abuse among others. Koechlin actively participates in the P & G Shiksha campaign for educating children living in rural parts of India. She participated in the 2015 Mumbai Marathon, a charitable event that aimed to spread awareness about issues such as: education, health issues like cancer and AIDS, and senior citizen welfare, accompanied by Shonali Bose's cousin Malini Chib. Having gone through sexual abuse at the age of nine, Koechlin aims to spread awareness around the issue, saying that it was, "important that parents remove the taboo around the word sex or private parts so kids can speak openly and be saved from potential abuse". She also spoke at the All Indian Conference for Child Sexual Abuse organised by actor Rahul Bose's non-governmental organisation HEAL.
Koechlin is a celebrity endorser and has been associated with several brands and services, including: Coca-Cola, Olay, Vogue, Micromax, Titan, Grey Goose's Style du jour, and AOC International including the cosmetic giant Oriflame. In an interview for Asian News International, Koechlin said that she "believes that everyone, whether an actor or a model, should endorse a brand which matches their ideologies". She was also the brand ambassador of the "Cinema For Care" section, aimed at creating awareness about disability issues at the All Lights India International Film Festival (ALIIFF) held in Thiruvananthapuram, Kerala in November 2015.