The union Unite organised the rally at the firm's headquarters in Derbyshire.
The union has called for an end to "Victorian working practices" and demanded staff get a living wage of Â£7.85 an hour.
Sports Direct said casual workers receive holiday and sick pay, and are included in incentive schemes.
The protest at the company headquarters was one of about 40 being held on Wednesday, with Sports Direct shops across the country also being targeted.
A Sports Direct spokeswoman said: "Much of the comment around the group's use of zero hours has been unfounded and inaccurate.
"The group complies fully with all legal requirements which relate to casual workers, including holiday and sick pay and freedom to gain other employment.
"Casual workers also benefit from general incentive schemes."
Unite said an estimated 3,000 workers are on zero-hour contracts at Sports Direct's Shirebrook headquarters.
A further 75% of staff across its UK stores are also on zero-hour contracts, with Sports Direct accounting for a fifth of all such contracts in the retail sector, according to Unite.
One institutional investor, Royal London Asset Management, earlier called for the resignation of Sports Direct founder Mike Ashley citing anger on his failure to attend four board meetings.
Ashley Hamilton Claxton from Royal London Asset Management, said: "We have lost confidence in the board and are very concerned about the long list of corporate governance failings that have not been addressed."
But both Mr Ashley and Sports Direct chairman Keith Hellawell were re-elected to the board at the meeting.
Unite representative Cheryl Pidgeon said: "We want an end to zero-hour contracts - because young people cannot stand 'forever and a day' to be on zero-hour contracts.
"We think Sports Direct makes enough money to ensure that their workers have to dignity, respect and fair wages."
A Dickensian-style protest has been held to oppose Sports Direct's use of zero-hour contracts at the company's annual general meeting.