Display omitted •Both Spathius agrili and Tetrastichus planipennisi were recovered in Maryland.•Only T. planipennisi has established and dispersed in Maryland.•Parasitism by T. planipennisi was positively associated with number of years post-release.•An exponential decrease model was fitted to the relationship between T. planipennisi parasitism and tree size. Classical biological control can be an important tool for managing invasive species such as emerald ash borer (EAB), Agrilus planipennis Fairmaire. Emerald ash borer was first detected in Maryland in 2003, and the biological control program to manage this beetle in Maryland was initiated in 2009. Here we examine the establishment and abundance of two introduced parasitoids of EAB larvae (Spathius agrili Yang and Tetrastichus planipennisi Yang). Overall, 56,677 S. agrili and 191,506 T. planipennisi were released at 26 and 32 sites, respectively, from 2009 to 2014. Monitoring parasitoids involved debarking trees, and harvesting trees to place in rearing barrels, and was conducted at 47 sites (23 of which received parasitoids, and 24 of which served as controls) from 2010 to 2015. We recovered 77 S. agrili from 16 EAB larvae at six sites, and 1856 T. planipennisi from 110 EAB larvae at 19 sites. Percentage parasitism by T. planipennisi, and the mean percentage of trees containing T. planipennisi broods, were positively associated with the number of years post-release of the parasitoids (reaching 11.6% and 41.7% four years post-release, respectively). The relationship between T. planipennisi parasitism and tree size was best described by an exponential decrease model, with over 95% of parasitism occurring in trees with a diameter at breast height of <16cm. In conclusion, T. planipennisi has established populations and dispersed in Maryland, while S. agrili releases have been largely unsuccessful. These findings are a step towards optimizing EAB biological control release and recovery strategies, and are particularly pertinent for other states in the Mid-Atlantic region.