Deitch was already 30 years old when he began his first job in the field of animation, working for the iconic animation house UPA, soon becoming a successful animator and opening his own animation studio. He moved to Prague to work on his own animated film Munro. There he met a young Czech animator, Zdena, whom he later married. Munro went on to become the first animated short film not made in the USA to win an Oscar.

Deitch worked on the American TV cartoon series Popeye and Tom and Jerry. He worked extensively with the Czech animation house Bratři v Triku. He directed more than 100 films during a career that lasted more than 50 years. Deitch and his wife were regular fixtures at Czech animation festivals, where both were honoured for their work and contribution to Czech animation.