Though less likely to be the direct cause, corrupted Visual C++ packages can lead to DLL errors. You can download and reinstall the latest versions directly from Microsoft.
The steamapi64.dll file is a critical digital link. It connects your game to the Steam client. It handles achievements, player profiles, and game verification. The two main reasons it goes missing are: steamapi64dll missing wwe 2k15 link
This is the only "official" method recommended by Steam and 2K Support. Do not download DLL files from the internet. Though less likely to be the direct cause,
If you purchased WWE 2K15 through Steam, do not download a .dll from the internet. Use Steam's built-in repair tools. It connects your game to the Steam client
Does this error happen with , or just WWE 2K15? Share public link
Download the steam_api64.dll (64-bit version) from the link above. Extract the file. Copy the steam_api64.dll file.