Havent used blender in a while but if you just need to join the objects then sure you can, see this answer on blender.se: https://blender.stackexchange.com/questions/2632/how-do-i-make-multiple-blender-objects-into-one#2633How do I make multiple Blender objects into one?
If you want to do other kinds of joining you might have a look into booltool for blender or join the objects first and then edit the resulting object yourself.