Obviously test, but yes it's fine to do so. You'll need to use the conv1011 utility to upgrade the database.
But there are other considerations. AI will need to be re-initialised, so you'll want to backup before and after. You'll need to recompile all code. Plus, if your data is in type I storage areas, now is a good time to consider a dump and load to move to a new structure involving Type II storage.
Some years ago we migrated from 10.1C to 11.3.1 without issues.
There was only 1 gotcha:
Originally we planned to upgrade all Windows clients (some 1500 PCs and a handful of Citrix servers) first and when done upgrade the Solaris servers a few weeks later. Since we use the client principal object to authenticate against the database we found out that they were not compatible between releases. So we had to provide both versions of our Windows clients and uninstall the old version when the upgrade on the Solaris servers was done. It took us more administrative overhead than we would have liked but in the end it worked out well without any issues.