The club's initial public offering share price of $14 enjoyed a brief, minor rise before falling back to its original price by the close of the day on the US market
The club had originally hoped to sell shares for between $16 and $20, but eventually opened trading at $14.
That price would still make the club the most valuable sports franchise in the world, with the $2.3 billion total exceeding the record $2 billion paid for the Los Angeles Dodgers.
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 euros as of March 31 – and its 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 materialize.
Analysts have warned that the club is 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.
"There was a lot of wing flapping, but not much flying today," John Fitzgibbon, the founder of IPOScoop.com, according to the Associated Press. "It's reflective of the overall IPO market, they may hit a couple of road bumps, but the deals are getting done."
United is aiming to sell around 16.7 million shares – approximately 10 percent of the club.
Most of one half of the offering - $101.7 million out of $110.3 million – 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.