TOKYO— SoftBank Group Corp. is on track for its worst annual performance in its 39-year history as the tech conglomerate said it expected to lose nearly $17 billion in its Vision Fund for the fiscal year just ended.

The investment loss means the $100 billion fund, the world’s biggest tech investment vehicle, is likely down since its launch three years ago. That would erase the billions of dollars in gains that the fund touted after investments like Uber Technologies Inc. and WeWork soared.

SoftBank blamed the loss on a “deteriorating market environment” that undercut the valuations of the Vision Fund’s portfolio companies. The downturn also helped push the Japanese company into an expected operating loss of $12 billion and net loss of $7 billion for the year ended March 31, SoftBank said Monday, adding that the results could change as figures are finalized.

The collapse of returns is one of the biggest blows yet for the Vision Fund as well as its charismatic creator, SoftBank Chief Executive Masayoshi Son.

SoftBank shares are down nearly 30% over the past year. They traded recently as low as one-third the value of its assets, according to Sanford C. Bernstein analysts.