Police said they were acting on the orders of the Punjab provincial government, which has vowed to prevent Mr Sharif's wife, Kulsoom Nawaz, from leading a procession from Lahore to Peshawar on Saturday.
Dozens of Pakistan Muslim League (PML) leaders and activists were locked up by the police, as others went into hiding.
Officials said about 165 PML members had been arrested; PML leaders said as many as 300 had been detained. They reportedly include Ahwaja Ahsan, the former lord mayor of Lahore.
"Police came to my house, picked me up and threw me in the lock-up," said one PML activist, Sheikh Majeed, quoted by the French AFP news agency.
"I don't know what the charges are and I'm not wanted for any criminal activity," he added.
The Punjab Governor, Mohammad Safdar, has vowed to stop Kulsoom's planned rally, in line with a ban on public political gatherings imposed by the military authorities.
"Under the law, you can hold a meeting within four walls but not rallies, as planned by her," he said.
Kulsoom defiant
Sources close to Kulsoom said she was aware of the crackdown, but was determined to go ahead with the planned procession of vehicles on Saturday.
Kulsoom said the aim of the motorcade was to raise money for people in the drought-hit provinces of Sindh and Baluchistan.
The BBC's Islamabad correspondent, Owen Bennett-Jones, says that so far there have been no significant street protests opposing the military authorities.
But by detaining so many PML activists in Lahore the authorities have signalled their determination to prevent such any protests getting under way, he says.
Kulsoom's public profile has grown since Mr Sharif was toppled in the October military coup and subsequently jailed for terrorism and hijacking.
In May, she led a motorcade to celebrate the second anniversary of Pakistan's nuclear tests.
Kulsoom's outspoken criticism of the military authorities has drawn angry attacks from the government and alienated some sections of the PML.
She has complained that many elements in the PML have not supported her, but rather have opted for a policy of non-confrontation with the army.
Mr Sharif is currently on trial for alleged tax evasion in connection with a private helicopter purchase. He faces 14 years in prison if found guilty.
He has already been given a life sentence for terrorism and hijacking, in a separate trial.