Yes, the file size is limited while uploading:
Photo & video files cannot be larger than 1 GB. For files & documents the maximum file size is 3 GB for Light and Standard customers and 20 GB for myCloud Pro customers.
Please note that only photos and videos up to 200 MB are automatically uploaded with the autoback function of the mobile apps. If you would like to upload larger photos and videos via the app, you can do so manually. You can find more information here.