If you haven’t had previous issues with this employee’s performance, I wouldn’t worry too much about his taking a second job. Side jobs are common, and many people manage them just fine. You can certainly reiterate your performance expectations, whether that’s completing assignments on time, immediately responding to messages, or meeting production quotas.
If at some point the quality of this employee’s work does begin to suffer, I would meet with him sooner rather than later to address the issue. A simple warning may be enough to get his performance back on track. Other options might include a performance improvement plan or a modified schedule that helps him better balance the two jobs.
Another consideration you might make is whether there are additional job opportunities at your place of employment that would appeal to this employee. Chances are he’s taken a side job to earn extra pay, expand his network, or enhance his work experience. Those may be goals you can help him achieve so he doesn’t have to look for work elsewhere.
Answer from Kyle, PHR:
Kyle is a professional author, editor, and researcher specializing in workplace culture, retention strategies, and employee engagement. He has previously worked with book publishers, educational institutions, magazines, news and opinion websites, nationally-known business leaders, and non-profit organizations. He has a BA in English, an MA in philosophy, and a PHR certification.