Retailers are facing a shrinking pool of workers as they staff up for the holidays, prompting some to offer more hours or higher pay to make sure they have enough cashiers or salespeople for the Christmas crush.

Toys “R” Us Inc. is giving part-time employees the chance to double their hours compared with a year ago. Macy’s Inc. is looking to turn more part-time jobs into full-time positions and Target Corp. is offering holiday workers more money for the busiest shifts.

“We’re...