According to the FSA's findings, Stewart McKegg and Brian Valentine Taylor held private stakes in Cardiff-based oil and natural gas exploration firm Amerisur Resources, then Chaco Resources.
In May 2007, both were contacted by the company's broker, who told them that a placing of substantially discounted Amerisur shares was due to be announced the following day. During these conversations, the men were told that this was confidential insider information.
However, following these conversations, the FSA said both men sold some or all of their existing Amerisur stock and replaced it with the shares issued below market price.
Tracey McDermott, the FSA enforcement division's head of wholesale, said the men had used the insider information to "take advantage" of shareholders who did not have access to it.
"Retail investors who are given inside information must observe, like any other market participant, the responsibilities this information brings," she added.
Mr McKegg was fined Â£14,411.25 ($21,561.19) and Mr Taylor was fined Â£4,642.50.