The option is worth an estimated $16.1 million for the 2016 season.
Miami is also reportedly focused on getting a long-term deal done with Tannehill done after locking up Pro Bowl center Mike Pouncey to a five-year contract extension worth $52.15 million.
Dolphins vice president of football operations Mike Tannenbaum said last month that he hopes that Tannehill is with the team for a long time.
Tannehill is set to make $660,000 in base salary, but will receive over $3 million in bonuses in 2015.
Tannehill has started every game for Miami since the team selected him with the eighth overall pick in the 2012 NFL draft.
Tannehill, who has a 23-25 record as a starting quarterback, set career highs in passing yards (4,045), completion percentage (66.4) and touchdown passes (27) last season for Miami, who have missed the playoff in each of the last six seasons.
- Scooby Axson