Backed by a financial windfall that has distributed extraordinary wealth throughout the N.B.A. this summer, the National Basketball Players Association will offer improved access to health insurance to more than 1,500 retired players.

The upgrade, made to part of the collectively bargained benefits package, was unilaterally enacted by the union and unanimously approved by player representatives at their annual summit meeting in late June. The union was expected to make an announcement about the decision later this week.

Under the new plan, retired players who were part of the league for at least three years can obtain a coverage plan that includes medical, hospital and prescription drug benefits. Retired players with longer tenures can have access to additional benefits, including spousal coverage.

The cost to the union for the new plan, the details of which are still being finalized, is expected to fall between $12 million and $15 million per year, according to a person with knowledge of the deal who was not authorized to publicly discuss the terms.