The tape featured four tracks Jones recorded in the YMCA's bathroom under the name Tommy Scott and The Senators more than 40 years ago. It was sold at Christie's in London for about $5,000, the Western Mail newspaper reported Friday.
The Daily Telegraph said the tape represented the earliest-known recordings of the now-famous singer.
"These recordings have genuine historical significance as they mark the birth of the Tom Jones phenomenon," a Christie's spokesman told newspaper.
Liz Williams, president of the Pontypridd YMCA, told The Telegraph it was Jones's idea to use the bathroom to tape the songs.
"When it came to the recording, he wanted to use the toilets because he believed they had the best acoustics in the building," Williams said.