Amanda Tidmarsh, 52, from Brynna, was walking her two rescue dogs along the beach in Ogmore-on-Sea when she noticed the bottle mixed up with seaweed.
She said she was "so excited" to find it, having previously joked with her family that she was "always on the hunt for treasure".
She is waiting to hear back from the crab fisherman who threw it overboard.
Canada is more than 3,000 miles (4,800km) from Wales, and the co-ordinates written on the letter show it was thrown in the sea nearby in November 2020.
Ms Tidmarsh said she was walking along the beach, in Vale of Glamorgan, with her labradoodle Daisy and Jack Russell Ollie when she saw the clear wine bottle, covered in barnacles, mussels and seaweed.
She said: "When I found it I thought it was lovely - got all this way without being smashed. I thought there was something inside it, it's like treasure."
She added she was "so excited" and thought it was "too special to open alone" so waited for her son to come home.
"I could believe it, it was really special. I text my other son and daughter as they were just as excited as me. It's unbelievable.
"I always joke to my mum that I'm looking for treasure amongst seaweed and I found some."
The note appears to be from a snow crab fisherman named John Graham, who left his email for the finder to contact him.
Crew on board that boat seem to have sent more than one message, as another bottle has washed up in County Kerry in Ireland.
"It was well sealed and inside was a zip lock bag rolled up with a note inside," said Ms Tidmarsh, who is optimistic to hear from the Mr Graham soon.
Meanwhile, the bottle is being kept in the greenhouse at her house in Rhondda Cynon Taf.
Photo Amanda Tidmarsh Caption: The dated letter has co-ordinates specifying where it was thrown into the sea