This is the third signing from the Patriots in the past few hours.
Tobin, 28, wound up signing on with the Eagles as an undrafted free agent out of Iowa back in 2013. He managed to make the 53-man roster each of his first two seasons in the NFL before signing a two-year extension with the Eagles in 2016.
The Eagles later traded Tobin and a 2018 seventh-round pick to the Seahawks in return for a 2018 seventh-round pick.
In 2017, Tobin appeared in 15 games for the Seahawks.