John Lorenza Cotton of Cypress spent thousands of dollars fighting legal battles in three countries to get back John Cotton Jr., who is now 8, the Orange County Register reported.
On Wednesday, Cotton flew to the Netherlands immediately after learning that Dutch authorities recognized his court-sanctioned rights to full custody of the boy.
The father raced to the U.S. Embassy to complete an expedited passport for his son and boarded the first plane out of Amsterdam.
"I am elated," Cotton told the newspaper upon his return to the U.S. early Thursday. "I knew this day would come. ... I am so happy this is finally over."
Cotton's effort to reunite with his only child was hampered by the fact that Zambia is not a signatory of the 1980 Hague Convention that requires countries to return abducted children to parents in other countries with valid court orders.
Cotton told the Register he caught a break in July when Cypress police Detective Greg Faessel learned that the boy had traveled with his maternal grandmother from Zambia to the Netherlands to visit an uncle. The Netherlands is a signatory of the Hague Convention.
With support from the Orange County district attorney's office, Cypress Police Department, FBI and U.S. departments of Justice and State, Cotton persuaded Dutch authorities to put a hold on his son's Zambian passport.
His ex-wife's lawyers tried to portray Cotton as an unfit and abusive father, but Dutch authorities abided by the Orange County court order and gave him back his son.
Cotton said he and John Jr. are bonding after having been separated for most of the past four years, during which time he was allowed little communication with the boy.
He told the newspaper that they have been promised counseling and other assistance from the National Center for Missing and Exploited Children.
Cotton also said he is enrolling his son in school in Orange County and plans to sign him up for youth soccer.
On the plane trip home, his son called him "Dad" for the first time since he was taken to Zambia in 2009. "It meant a lot to me," Cotton said.