Situated on Japan’s Honshu island, it is possible to visit Hiroshima from Osaka or Kyoto on a day trip. But there’s also enough to do to in this city that it might be worthwhile to extend your stay and spend the night.

Osaka to Hiroshima by Shinkansen Train
Yes, you can travel from Osaka to Hiroshima with a JR Pass on a shinkansen train. Hiroshima is just 1 hour and 40 minutes west from Osaka on the Tokaido-Sanyo Shinkansen train (which is covered in your JRail pass), making it a great place to visit on a day trip.

You’ll board the bullet train in Osaka at Shin-Osaka Station and ride west towards Hiroshima Station.
Osaka to Hiroshima by Bus
You can also find regular daytime and overnight buses from Osaka to Hiroshima. The buses will depart from Osaka Station JR Express Bus Terminal and take about 5 hours to reach Hiroshima. You can book your tickets directly at JR Expressway Bus Ticket Center on the 1st floor of Osaka Station. Fares will vary based on the service, but should be around ¥4,000 – ¥6,000.
Kyoto to Hiroshima
You can travel from Kyoto to Hiroshima on the shinkansen train lines as well. A direct journey between the two stations (Kyoto Station and Hiroshima Station) will take about 1 hour and 40 minutes.

However, if you are using your JRail Pass, you will have to book Hikari or Sakura services (Nozomi services are not included in the pass) and you may have to transfer at Osaka Station or Kobe Station. The good news is, this will only add 10-15 minutes to your total journey. Without the pass, you can expect to pay over ¥10,500 (about $100 USD) for a ticket to Hiroshima from Kyoto.
Tokyo to Hiroshima
You can use your JRail Pass to take the Tokaido-Sanyo Shinkansen train from Tokyo to Hiroshima. You’ll book a ticket from Tokyo Station and stop in either Osaka Station, Kobe Station or Himeji Station. The entire trip, including transfer, takes about 5 hours in total from Tokyo and will cost you upwards of ¥18,000 if you don’t have the JR pass.
Another option is to take a 90-minute flight on one of several domestic airlines connecting Tokyo to Hiroshima. The flight will cost you around ¥25,000 so a JRail Pass is easily your most cost-effective option. Especially if you plan to visit other destinations while in Japan.