[4] Hollein oversaw both the de Young and the Legion of Honor museums, which together are the seventh most-visited art institutions in the United States, with 1.4 million visitors in 2016.

He was also involved in fundraising, travelling exhibitions, the inauguration activities at Guggenheim Bilbao as well as liaising with European cultural institutions, collectors, media, curators and sponsors.

[7] He repositioned the Schirn Kunsthalle Frankfurt nationally as well as internationally through a highly popular yet challenging exhibition programme from classical to contemporary art mounting up to ten major shows per year.

Among the highlights of the programme have been exhibitions such as "Shopping: A Century of Art and Consumer Culture", "Henri Matisse: Drawing with Scissors", "Yves Klein", "The Naked Truth: Klimt, Egon Schiele, Kokoschka and Other Scandals", "Women Impressionists" and "Edvard Munch.

[18] Among the most significant projects worthy of mention in this context was the major expansion of the Städel Museum completed in 2012 which doubled the institution's gallery space and created a new wing for the presentation of art since 1945.

The Art of Ancient Egypt and Antiquities, Middle Ages, Renaissance, Baroque to Neoclassicism as well as the "studioli" on the top floor of the museum villa were newly installed under his tenure and reopened in 2008 with an entirely new color and lighting concept.

Exhibitions such as "Sahure – Death and Life of a Great Pharaoh", "Gods in Color ", "Franz Xaver Messerschmidt" were received with unprecedented attention.

[30] He also successfully launched a contemporary art initiative, bringing the work of living artists into dialogue with the buildings and collections of the de Young Museum and Legion of Honor, with exhibitions by Urs Fischer, Sarah Lucas and Sarah Lucas and Julian Schnabel at the Legion of Honor and Carsten Nicolai and Leonardo Drew at the de Young museum.

[32] Hollein opened several critically acclaimed exhibitions, including The Brothers Le Nain: Painters of Seventeenth Century France,[33] Frank Stella: A Retrospective,[34] Danny Lyon: Message to the Future,[35] Monet: The Earl Years[36] and Stuart Davis: In Full Swing.

[37] Ed Ruscha and the Great American West, Cult of the Machine, and The Summer of Love Experience: Art, Fashion, and Rock & Roll which drew almost 270,000 visitors and 400.000 online visits from around the world, making the exhibition[38] the highest attendance in recent years.Hollein expanded the de Young furthermore on the encyclopedic focus of its program, with exhibitions such as Teotihuacan: City of Water, City of Fire, The Maori Portraits: Gottfried Lindauer's New Zealand, and Contemporary Muslim Fashions.

Hollein also expanded the institution's educational outreach, including digital interactive tools to prepare for exhibitions, and the construction of the DeYoungster's Studio – a learning space that fosters children's curiosity and understanding of art.

[4] He succeeded in a selection process whose finalists included Adam D. Weinberg, Julián Zugazagoitia, Emilie Gordenker, Timothy Rub, and Taco Dibbits.

[52] Early in his tenure, Hollein said he would focus on further injecting modern and contemporary art into The Met's main Fifth Avenue building.

[55][56][57][58][59] In lectures Hollein shares that The Met will invest in the next ten years to update the gallery system, with a special emphasis on refreshing and recontextualizing its narratives.

[64] The move marks a return to the Met’s old leadership structure, wherein the director of the institution is responsible for both the programmatic direction of the museum as well as its day-to-day operations.