The free agent reportedly also received $2.5 million guaranteed.
Harris racked up career highs in sacks (six) and total tackles (49) last year in his third season with the Broncos (fifth overall). The 28-year-old also started 16 games for the first time in his career.
It's a surprisingly modest deal for Harris, who was projected by Spotrac to earn an annual salary of $12.3 million on the open market.
The veteran returns to a defensive line bolstered by Pro Bowler Jurrell Casey, who was acquired by the Broncos from the Tennessee Titans for a seventh-round pick last week.