The kayaker told lifeguards, who then found the young animal in distress in the waters about a mile off La Jolla on Friday.
With the help of SeaWorld experts, they were able to remove the netting from the dolphin's dorsal fin, using a pole to gather the 50- to 100-foot line.
SeaWorld mammal curator Keith Yip told local media that the cuts on the fins indicated the line had been rubbing against the 4-feet-long dolphin for weeks. He said the dolphin appeared tired and was probably not able to feed.
Once the dolphin was free, off it went! A news helicopter spotted it swimming to other dolphins that apparently stayed in the area.
The Associated Press contributed to this report.