Multiple projects using the same resources

Those multiple projects are they similar in terms of scope, deliverables and end product? If they are not, then get stakeholders of these projects to agree on using same resources, its terrible to be in this situation.

If you are only asking how to manage it within your scheduling tool, then you may want to research the use of resource leveling. Be aware that resource leveling can make changes that you may not like so it's important to fully understand how the settings work. In any case, you need to make sure you are assigning resources to activities with realistic durations and hours. Then when you view a resource-oriented view of the multiple projects together, you see any overallocated resources and can decide how to resolve them.

In my experience, resource leveling within a planning tool is not going to give you a solution you want. As the projects progress, there will be changes in priorities. Managing overallocated resources requires analysis and the PM's involvement to make the calls on how to resolve them.

Thank you James. Yes, I need to manage them within the tool but I can't find a resource-oriented view of the multiple projects together in MS Project. I'm still researching this. I was going to consider resource leveling but thanks for the advise for being cautious about it. What tool are you using for managing multiple projects?

We use Primavera to handle this but I believe you can do it in MS Project by using "subprojects" under a master project. This should allow you to have all the "subprojects" open at once - then switch to a resource sheet view. It will have all the tasks from the subprojects organized by resource - and it prepends the project name to each task name in brackets so you know what subproject it came from.