Yes, you can absolutely upgrade your Disney theme park ticket to a Park Hopper even after you have already entered your first park of the day. This is a common practice for guests who realize halfway through the day that they want to see the fireworks at a different park or join friends elsewhere. To perform the upgrade, you can visit any Guest Relations window or the ticket booths located at the entrance of all four theme parks. In 2026, you can often also do this directly through the My Disney Experience (for Florida) or the Disneyland app (for California) under the "Tickets and Passes" section, provided your ticket is linked to your account. It is important to remember that the cost to add Park Hopper is a flat fee for the entire length of the ticket; it is not prorated. This means if you have a 5-day ticket and you decide to upgrade on day 4, you will still pay the full price as if you had "hopped" for all five days. Once upgraded, you can typically hop to a second park at any time during park hours, subject only to the capacity limits of the destination park.