You can make one employee contribution no matter how many 401ks you have access to. As long as you make $20,500 you can put it all into a 401k. You cannot if you have more than one 401k you cannot put 20,500 into one, then put 20, 500 into a second and 20,000 into a third. The other type of contribution that can be made into that account beyond employer contributions are what are called after tax employee contributions. If there is another feature that the 401k offers, this can really be a great move for investors.