That first small building was expanded in 1916 to accommodate the growing area and renamed Middlesex General Hospital.

[4] At this time, the Department of Clinical Research was established, X-ray technologist training began, and the hospital auxiliary was founded.

[6] In 2014, Robert Wood Johnson University Hospital and Somerset Medical Center officially completed their merger.

The New Jersey Attorney General must review the deal before it is official, with the expectation that the merger would be completed in 2016.

[11] Made possible thanks to a lead gift from the Blanche and Irving Laurie Foundation as well as support from individual donors, it is currently home to the world's third MEVION S250 Proton Therapy System.

Proton therapy is part of a comprehensive range of advanced cancer treatment options offered by RWJ in partnership with Rutgers Cancer Institute of New Jersey (CINJ), Rutgers Robert Wood Johnson Medical School and private physicians in the community.

[15] Robert Wood Johnson University Hospital also features a Level 1 Trauma Center, 1 of 4 in New Jersey.

[2] The American College of Surgeons' Commission on Cancer has rated RWJUH among the nation's best comprehensive cancer centers and the hospital's Comprehensive Stroke Center is certified by the Joint Commission to provide complex stroke care.

[16] Harvard University researchers, in a study commissioned by The Commonwealth Fund, identified RWJUH as one of the top-ten hospitals in the nation for clinical quality.

[28] Robert Wood Johnson University Hospital Somerset, a RWJBarnabas Health facility, is a nationally accredited, 297-bed[29] regional medical center providing a variety of comprehensive emergency, medical/surgical, behavioral health and rehabilitative services located in Somerville, New Jersey.

Robert Wood Johnson University Hospital Hamilton also features state designated Primary Angioplasty Site.

[15] Robert Wood Johnson University Hospital also features an emergency department for area residents.

It is affiliated with both Robert Wood Johnson Medical School and PSE&G Children's Specialized Hospital, and is a member of RWJBarnabas Health.

The hospital provides comprehensive pediatric specialties and subspecialties to infants, children, teens, and young adults aged 0–21 throughout New Jersey.

[45] In 2019, officials from RWJBarnabas announced that plans were made to construct a new 12 story, $750 million cancer hospital across the street from RWJUH.