Mr. Ambode assented to the bill on Wednesday at the Lagos House, Alausa, Ikeja.
The law provides for death penalty for kidnappers whose victims die in their custody, and life imprisonment for the act of kidnapping.
The News Agency of Nigeria reports that the Lagos State House of Assembly passed the bill on January 5.
The governor said that the law was enacted to address key issues bordering on security.
He said that kidnapping had become a major threat to the safety of residents and, therefore, required decisive action by the government.
“This law imposes a penalty of life imprisonment for kidnapping for ransom.
“The law stipulates that, where a victim dies in the course of kidnapping, the suspect is liable on conviction to death.
“Security is of utmost importance to our administration, and we are confident that this law will serve as a deterrent to anybody, who may desire to engage in this wicked act within the boundaries of Lagos State.
“Our justice system will be required to execute this law to the letter and make sure that any criminal caught faces the full wrath of the law,” he said.
“What we are doing in respect of kidnapping is in good spirit so that we can eradicate it completely from Lagos,” Mr. Ambode said.
Mr. Ambode also signed into law, the Lagos State Sports Commission Bill and the Lagos State Trust Fund Bill.
He said that the Sports Commission Law would give legal backing to formulation and implementation of sports policies in the state, while the Sports Trust Fund Law would enable the state government to raise money for development of sporting facilities and activities.
He said that the fund would provide a platform where the government could enter into partnership with the private sector to finance sports infrastructure, tournaments and programmes.
Mr. Ambode said that this would create employment and generate revenue for the state.
“As provided for in the law, a board of trustees comprising all stakeholders in the sports community will be inaugurated soon to manage the Sports Trust Fund.
“By these laws, we have restated our commitment to sports and making Lagos the hub of sports in Nigeria.
“The passing of these laws has been made possible by the commitment and dedication of the Lagos State House of Assembly,” he said.