The condition of the four after being freed has been unclear, however, the Christian organisation World Watch Monitor says they're reportedly "in good health".
Found guilty of "inciting religious violence" Gifti, 14, Mihiret, 14, Eden, 15, and Deborah, 18, began their sentences on 25th November 2016 and were released on 22nd December.
They were distributing a book entitled 'Let's speak the truth in love: Answers to questions' by Ahmed Deedat in the town of Babile in Harari, a region with a significant Muslim population.
Local Muslims claimed the book insulted Islam and the four were arrested, while the incident prompted attacks on two churches on 19th September last year.
World Watch Monitor said: "Ethiopia's constitution guarantees freedom of religion, but Christians who formerly adhered to Islam can face discrimination, threats and sometimes attacks."
According to Open Doors' 2017 World Watch List of countries where persecution against believers is fiercest, Ethiopia is ranked 22nd.