Yes, the journey from Interlaken Ost to Grindelwald is 100% covered by the Swiss Travel Pass in 2026. This route is operated by the Berner Oberland Bahn (BOB), and as a standard regional train, it counts as part of the "unlimited travel" benefit of the pass. You do not need to purchase a separate ticket or make a reservation; you simply board the train and show your digital pass to the conductor. However, be aware that once you reach Grindelwald and wish to travel higher into the mountains—such as taking the Eiger Express to the Eigergletscher or the train to the Jungfraujoch (Top of Europe)—the Swiss Travel Pass only provides a 25% discount rather than full coverage. The pass is excellent for the "valley" connections like Interlaken-Grindelwald or Interlaken-Lauterbrunnen, but requires supplemental "top-up" tickets for the high-altitude cable cars and cogwheel railways.