Osmotic pump systems require prolonged retention time in the stomach to provide enhanced bioavailability and regulated release, which is quite challenging. This study used a three-dimensional printing (3DP) technique combined with a gastro-retentive floating device (GRFD) to extend the retention of the osmotic pump in the stomach and enhance its bioavailability. The strap-on buoyant device was fabricated by stereolithography 3DP and incorporated a felodipine osmotic pump tablet used in clinical practice, which enabled it to float in the stomach or dissolution media without any floating lag time. The components of the device were affixed using a snap-fix mechanism. GRFD dissolution study revealed a notable in vitro floating capability, lasting over 24 h, with a release profile similarity factor f = 65.28 compared to the naked tablet dissolution profile. The pharmacokinetics of felodipine osmotic pump in beagles showed a C of 1.893 ng/mL, which increased to 4.511 ng/mL with GRFD. The delivery of an osmotic pump with GRFD enhanced the AUC of felodipine from 10.20 ng/mL·h to 26.54 ng/mL·h. In conclusion, the strap-on buoyant device has been successfully designed to enhance gastrointestinal tract retention of felodipine osmotic pumps and bioavailability in beagles.