Speaking in a hotel banquet room to scores of delegates who are traveling with the governor, Brown said his trip "is not your ordinary trade mission."
"This is serious," he said. "There's a lot we can do on some of the most important issues the world faces."
The governor has prioritized addressing issues such as climate change, and he's expected to sign an agreement with Mexican officials on the matter on Monday afternoon.
In addition, Brown's Monday agenda was modified to include a private meeting with Mexican President Enrique Peña Nieto. He's also scheduled to meet with the governor of the state of Mexico and the foreign affairs secretary. A reception with the U.S. ambassador is to be held at a downtown art museum.
On Tuesday, Brown is expected to address the controversy concerning Central American migrants, particularly unaccompanied children, entering the United States. He's scheduled to meet with the Los Angeles archbishop and leaders from Central America.
The governor, who has called the issue a "humanitarian question," has sought to position California as a more welcoming place for immigrants, including those in the country illegally. He's signed legislation allowing them to obtain driver's licenses and reducing the number of situations in which arrests by local law enforcement triggers deportation proceedings.
Before entering the reception on Sunday, Brown told reporters that California's record on immigration will boost the state's success south of the border.
"Because of our proximity, and our history, and also our sympathetic policy both to Mexico and to the plight of people who have struggled to get [to California] from Mexico," he said, "we are in a very good position to forge very close and productive relationships."