She was selected out of 153 applicants and seven finalists, who were interviewed, the city manager's office reported.
Keene said Antil's hiring is part of a broader reorganization of his office.
"Pam brings the right qualifications, great energy and exemplary 'people' skills to help us through these challenging times," Keene said in a statement announcing her hiring.
The City Council is expected to ratify Antil's appointment Monday night.
The position has been vacant since May 2008 following the resignation of former Assistant City Manager Emily Harrison, who took a job as a deputy county executive for Santa Clara County.
The assistant manager serves as the operations officer for the city and "may act on behalf of the City Manager when necessary at City Council meetings and in other high-level capacities," the announcement stated.
Antil's salary will be $195,000 a year.
"Filling the position at this time is critical to the effective operations of the City and our ability to help transition our organization through challenging times while fulfilling Council priorities," Keene wrote in his report to the council.
Antil has more than 20 years of management experience and has worked on implementing "green" initiatives and energy savings in Novi, Mich., where she has served as assistant city manager since 2006. Before that, she served as assistant city manager at Ann Arbor, Mich., and at Rancho Palos Verdes in Southern California.
She received a master's degree in public administration from California State University, Long Beach, and has served on numerous committees for the International City/County Management Association.
"My husband and I are very excited to be able to raise our girls in Palo Alto and be fully engaged in the community through my work within the city organization and our family's involvement in the schools and civic groups," Antil said in a statement.
Keene touted Antil's prior experiences as an assistant city manager and said he is "looking forward to Pam helping with the city's day-to-day operations."
Kelly Morariu, assistant to the city manager, said Antil's hiring is one component of a broader restructuring of Keene's office.
Susan Barnes, Keene's assistant for economic development, will retire in June after 11 years with the city.
The duties of promoting economic development will be assumed by Deputy City Manager Steve Emslie, who will oversee the new Office of Economic Development. Last year, the city manager's office hired Debra van Duynhoven to serve as its sustainability coordinator, replacing three part-time environmental coordinators who have other jobs with the city.
Keene is also planning to appoint Greg Betts the director of the Department of Community Services. Betts, who has served as a manager in the department for 26 years, currently fills the director position on an interim basis.
The council is scheduled to ratify Betts' appointment and Antil's contract at its meeting Monday night (March 8).