Paul West's suit seeks class-action status for 10,000 pension-plan participants, according to Bloomberg.
WellPoint shares have slumped 45 percent this year, to about $50.
In a response to IBJ, WellPoint said it is confident it acted prudently and appropriately with the 401(k) plan, and that it offers employees the option of investing in WellPoint stock.
Matching contributions to the plan are made in cash, not stock, WellPoint said.
"WellPoint is confident that there is no legal or factual basis for the claims asserted in the West complaint," the company said in a statement. "We will vigorously defend ourselves in this matter."