The 30-year-old had been attracting plenty of attention after leaving Castleford, having also played for Wigan and Huddersfield, but has now signed a 12-month deal with the Airlie Birds.
The powerful forward has revealed that there was never any doubt over his future once he discovered that Hull were keen.
"Once I was told of their interest, that was the place I wanted to go," Aspinwall told the club's official site.
"They have signed some good players, there is a new coach, a new regime and it all seems very positive from the outside so it seemed like the right move for me and something I wanted to be part of.
"It's very humbling and a privilege to be part of this club, with the tradition and the history they have got.
"It's a massive club - the fan base, the facilities, the stadium - and now with a new regime in place that are desperate to take the club forward everything is positive and it's something any player would want to be part of."