According to the United States Census Bureau, the city has a total area of 144.9 km² (55.93 mi²). 144.85 km² (55.7 mi²) of it is land and 0.6 km² (0.2 mi²) of it (0.45%) is water.

Prior to development, the land that became Palm Beach Gardens was primarily cattle ranches and pine forests, as well as swampland further west. In 1959, wealthy landowner and insurance magnate John D. MacArthur announced plans to develop 4,000 acres (16 km²) and build homes for 55,000 people. He chose the name Palm Beach Gardens after his initial choice, Palm Beach City, was denied by the Florida Legislature, because of the similarity of the name to the nearby Palm Beach. MacArthur planned to build a "garden city" so he altered the name slightly. The city was incorporated as a "paper town" (meaning that it existed only on paper) in 1959. The 1960 Census recorded that the city officially had a population of one, apparently a squatter whom MacArthur had allowed to stay on his property.

Rapid development took place in the 1960s. By 1970 the city had a population approaching 7,000 people. To showcase his new community, MacArthur purchased an 80-year-old banyan tree located in nearby Lake Park, that was to be cut down to enlarge a dentist's office. It cost $30,000 and 1008 hours of manpower to move it. A second banyan was moved the following year. While moving the first banyan tree over the Florida East Coast Railway, the massive tree shifted and disconnected the Western Union telephone and telegraph lines running adjacent to the railroad, cutting off most communications between Miami, 80 miles to the south, and the outside world until the damage could be repaired. These trees still remain at the center of MacArthur Boulevard near Northlake Boulevard and are still featured on the city shield. In January 2007, the great-grandson of impressionist artist Pierre-Auguste Renoir, Alexandre Renoir, presented a painting to the city which depicts the Gardens banyan tree. It is currently on display at the city hall on North Military Trail.

City growth was slow but steady throughout the 1970s and 1980s, as the population has still not reached the predicted 55,000 people envisioned by MacArthur. However, the opening of the 1.3-million-square foot Gardens Mall in 1988 initiated a new wave of development, as did the sell off in 1999 of approximately 5,000 acres (20 km²) in the city by the John D. and Catherine T. MacArthur Foundation. Development of this property happened quickly and led to much new growth in the city. The city adopted an Art In Public Places ordinance in 1989 and has amassed an eclectic collection of works.

The city suffered much damage to its tropical landscaping in the hard freezes of 1985 and 1989, but has experienced no freezing temperatures since then. The city was hit by Hurricane Frances, Hurricane Jeanne, and Hurricane Wilma in 2004 and 2005. Much of the city lost power for days at a time after each storm, and many traffic signals and directional signs in the city were destroyed. Many homes and businesses were severely damaged during the first two storms and contractors and construction materials were at a premium. Hundreds of homes were only nearing final repair when Hurricane Wilma hit the following year damaging or destroying many of those completed or ongoing repairs.

The Professional Golfers' Association of America has its headquarters in the city. There are 12 golf courses within the city limits, including a course owned by the municipality. Several PGA tournaments have been hosted in Palm Beach Gardens since 1971. The Honda Classic has been held at the PGA National Resort and Spa since 2007 and was held at the Country Club at Mirasol from 2003 to 2006; both are located in Palm Beach Gardens. Ameribank and Wackenhut also have their headquarters in Palm Beach Gardens. The Gardens Mall, PGA Commons, Legacy Place, and Downtown at the Gardens are the center of the city's retail market. The city has the first and one of only three Paul bakeries in the United States.

Public K-12 primary and secondary schools are administrated by the School District of Palm Beach County. Palm Beach Gardens Community High School and William T. Dwyer High School are the local public high schools. The Upper School campus of The Benjamin School is also located in Palm Beach Gardens.

The Edward M. Eissey Campus, a satellite campus of the Palm Beach State College, is located in Palm Beach Gardens. It includes the Eissey Theatre for the Performing Arts.

As of the census of 2000, there were 35,058 people, 15,599 households, and 10,217 families residing in the city. The population density was 243.1/km² (629.6/mi²). There were 18,317 housing units at an average density of 127.0/km² (329.0/mi²). The racial makeup of the city was 93.78% White (89.1% were Non-Hispanic White,) 2.30% African American, 0.11% Native American, 2.15% Asian, 0.03% Pacific Islander, 0.67% from other races, and 0.96% from two or more races. Hispanic or Latino of any race were 5.63% of the population.

There were 15,599 households out of which 23.4% had children under the age of 18 living with them, 53.8% were married couples living together, 8.9% had a female householder with no husband present, and 34.5% were non-families. 27.7% of all households were made up of individuals and 10.5% had someone living alone who was 65 years of age or older. The average household size was 2.23 and the average family size was 2.70.