The German utility on Wednesday (February 28) blamed lower wholesale energy prices for the outlook.
The company has forecast adjusted net profit of between $758 million and $1.2 billion - well down from last year's record $4.8 billion
The outlook reflects a normalization of wholesale power and gas prices, which rose sharply when Europe severed most energy ties with Russia.
The update follows other leading energy firms, including EDF, in warning about lower profit this year.
Uniper was rescued by the German government at the height of Europe's energy crisis two years ago.
It needed a more than $14 billion bailout after Moscow stopped gas supplies via the Nord Stream pipeline.
That forced the company to buy replacement volumes at sky-high prices.
The German government owns more than 99% of Uniper.
Sources last month said it was considering releasing an up to 30% stake in a listing next year.
Investors were put off by Wednesday's update and Uniper's shares were down over 7%.
