"Investor sentiment and market performance have typically driven some of the scores in this survey," chief executive Rob Everett said in a statement.
"It is heartening to see that confidence, while dipping slightly, has been broadly stable in the event of significant issues both offshore and in local financial services."
The regulator's survey matches similar stability in ASB Bank's latest investor confidence report, which increased to a net 21 per cent optimism in the June quarter from 20 per cent in March.
Like consumer confidence, ASB's gauge of investor sentiment has remained relatively upbeat in contrast to the growing pessimism among businesses, and Acting Prime Minister Winston Peters has taken to pointing to recent records on the S&P/NZX 50 index as a better gauge of business sentiment.
About 84 per cent of survey respondents had at least one investment in New Zealand's markets, with KiwiSaver the most common at 63 per cent.
Still, KiwiSaver-only investors were less knowledgeable about investment principles such as diversifying a portfolio and understanding that a bigger return typically accompanies a higher risk.
About two-thirds of investors received investment materials, although just 55 per cent found them useful in making an informed decision, a level which has been relatively static over the six-year life of the annual survey.
Awareness of the regulator was stable at 41 per cent, although confidence that markets were being effectively regulated shrank to 55 per cent from 66 per cent a year earlier, with a 9 percentage point increase in people saying they didn't know. The FMA survey said that swing was probably down to a change in how the question was asked.