No, you cannot use a Prefect 3.x deployment with a Prefect 2.x worker. The version changes between Prefect 2.x and 3.x introduced significant architectural changes in how deployments and workers function. You'll need to ensure that both your deployment and worker are running the same major version of Prefect. If you're planning to use Prefect 3.x deployments, you'll need to: 1. Upgrade your worker to Prefect 3.x 2. Configure your worker to use the new work pool system introduced in 3.x If you need to maintain Prefect 2.x workers for some reason, you should continue using Prefect 2.x deployments with those workers. However, I'd recommend upgrading your entire infrastructure to 3.x when possible to take advantage of the improved deployment and worker system. Would you like more information about upgrading from 2.x to 3.x, or about setting up workers in either version?