The disclosed computer-implemented method for secure hybrid third-party data storage may include (1) identifying, at a trusted proxy system, an access request from a client system to access an encrypted file stored under a user account at a third-party storage system, where the requested access requires decryption of the encrypted file, (2) retrieving, from the third-party storage system, (i) the encrypted file and (ii) a decryption key that has been encrypted with a client-side key, where an asymmetric key pair designated for the user account includes an encryption key and the encrypted decryption key, (3) receiving, at the trusted proxy system, the client-side key, (4) decrypting, at the trusted proxy system, the decryption key with the client-side key, and (5) using the decryption key to access an unencrypted version of the encrypted file at the trusted proxy system. Various other methods, systems, and computer-readable media are also disclosed.