Roseanna Cunningham has written to the UK government seeking assurances over the clean-up of the Caithness coast site.
The Scottish Environment Protection Agency gave an end-of-year “at risk” rating for the management of radioactive waste and a “poor” rating for management of low level waste vaults.
And a recent annual report of the Nuclear Decommissioning Authority reported a “deterioration” in safety performance.
In a letter to Energy Minister Richard Harrington, Ms Cunningham said: “I would like to raise concerns about performance at the Dounreay site and seek your assurance the UK government is giving sufficient attention to Dounreay. There continues to be cause for concern in Dounreay’s environmental performance.
She said the situation was disappointing and sits oddly with the expected loss of around 200 jobs at the site.
A spokesman for the UK Department for Business, Energy and Industrial Strategy said it would respond to the letter “in due course.”