Subject to clearance from the Pakistan Cricket Board, the pace bowler will join up with the Division Two outfit in July, following his country's tour of the West Indies.
Moody said Akhtar would be a valuable weapon as the county seeks a return to the top flight of English county cricket following relegation this year.
"Shoaib is a world-class strike bowler in both forms of the game and he will spearhead our drive for success in the latter half of the season," Moody said on Wednesday.
"His experience of county cricket can only be an advantage to us at New Road. He creates a huge buzz wherever he bowls and I have no doubt Shoaib will be a popular member of the squad both on and off the field."
Akhtar, who has previously played in England for Durham, said in a statement that he was relishing the challenge of playing for Worcestershire.
"I love playing county cricket in England and I'm really looking forward to helping Worcestershire get straight back into Division One of the championship and challenge for honours in the one-day game.
"I'll be rested and raring to go when I start in July and, from looking at the players Worcestershire have in their side, confident we'll have a successful season."