Human resources strategies: When handling employee complaints, do I address the individual causing the issue directly or talk to their manager first?

A strong grievance management proceedur follows the principles of Natural Justice which says "hear both the sides " The HR manager performs the role of an arbitrator and should not only be fair but also seem to be fair

While handling employee complaints, the individual causing the issue should be talked with first and then his/her manager. but it must be ensured that both the sides are heard and given due attention.

The direct manager is notified and the employee causing the problem is called directly to investigate.

Proper procedure requires Manager to submit incident report with affix signature from employee/ employees involved with an explanation / dissenting opnion if employee /employees might believe that report was in-accurate.Thus,it is imperative to issue a show order for all ( at the same time ) to judge the issue objectively.

Please note that for every regular employee having called for office / hr is an intimidating unpleasant situation unlike Manager employee felt powerless. So nuetral ground is very important.

As for the Manager, he/her report should be treated as final statement and must refrain from giviing unsolicited judgement.    

For sure you shoud talk to immediate manager first. follow the heirarchy