The club had originally hoped to sell shares for between $16 and $20 (£10-£12), but eventually opened trading at $14 (around £9).
That price would still make the club the most valuable sports franchise in the world, with the $2.3 billion total exceeding the record $2bn paid for the Los Angeles Dodgers baseball team.
The shares briefly rose to a price of $14.05 but ended the day trading at the same $14 valuation that they had been offered at.
The disappointing opening day has been put down to the debt load on the club – United carried £416.7 million as of March 31 – and their financial track record.
Many had expected that enthusiasm for the world-renowned team, particularly among fans, might lead to a bright start in trading but that failed to materialise.
Analysts have warned that the club are still overvalued despite the reduction that has already taken place due to the debt load and the voting control that the Glazer family, who own them, will retain.
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United are aiming to sell around 16.7m shares – approximately 10 per cent of the club.
Most of one half of the offering - $101.7m out of $110.3m – will be used to pay down senior debt, while the other half will be sold separately by the Glazer family.
United vice-chairman Ed Woodward, meanwhile, claimed that the club opened at the lower price to attract higher quality investors.
"The huge number of high-quality institutional investors that were there at $14 just made us more comfortable in terms of the longer-term view here, with regard to the type of investor base we wanted," he told the BBC.