In 2017, he starred as teenage Ethan Montgomery in the comedy-drama film A Dog's Purpose, which was released on the same day as Riverdale premiered on television. Apa's next film role was replacing Kian Lawley in the 2018 drama film The Hate U Give. Apa starred as Griffin in the Netflix film The Last Summer, which was released on 3 May 2019. He also starred as singer Jeremy Camp in the biographical romantic drama film I Still Believe, which was released in March 2020.
Apa was involved in a minor car accident in Vancouver in September 2017, but was uninjured when the passenger side of his car hit a light pole. The event was reportedly the result of Apa falling asleep at the wheel after a long day of shooting the previous night.