Twitter Inc.’s TWTR 7.09% high-profile debut live-streaming a National Football League game went off without a glitch Thursday night, but low viewership numbers indicate that most football fans still prefer to watch the game on traditional TV.

An average audience of 243,000 viewers per minute watched the New York Jets beat the Buffalo Bills via a live-stream broadcast on Twitter, according to the NFL. That pales in comparison with the average of 15.4 million people who watched the game on CBS and the NFL Network.

Twitter’s viewership is also lower than the 2.36 million people per minute who watched Yahoo Inc.’s live-stream of the Jacksonville Jaguars and Buffalo Bills game last October, a game played in London and broadcast early Sunday morning in the U.S. and that automatically played across Yahoo’s properties.

Each viewer on Twitter watched an average of 22 minutes of game action, the NFL said, nearly in line with the 25-minute average digital viewership of the game across Twitter and digital offerings from Verizon Communications Inc., the NFL Network and CBS.

In total, the NFL said 2.1 million unique viewers world-wide tuned into the live game broadcast via Twitter, watching it for at least three seconds with the video player in full view. CBS and NFL Network’s coverage received 48.1 million viewers for at least one minute of time.

The low viewership turnout on Twitter compared with traditional TV suggests that it may still take some time for people to get used to watching games on the go. According to NBC, the average audience for the live-stream of last Thursday’s matchup between the Carolina Panthers and the Denver Broncos available on the NBC Sports app, NBC.com ‘TV Everywhere,’ and NFL Mobile from Verizon totaled 278,000 viewers.

Twitter’s numbers leave something to be desired in light of the fanfare leading up to its first NFL game live-stream.

Thursday night’s game was a coming-out party of sorts for Twitter’s live-streaming strategy, the cornerstone of its plan to become the premier destination for live events. Twitter is trying to appeal to advertisers by capitalizing on its strength as a real-time service and the growing trend of cord-cutting viewers.

On the bright side, anecdotal evidence shows that viewers were generally pleased with Twitter’s stream of the CBS Corp. feed of the game between the New York Jets and Buffalo Bills. The live-stream of the game was available on Twitter’s mobile app and website as well as Apple Inc. ’s Apple TV, Amazon.com Inc. ’s Amazon Fire and Microsoft Corp. ’s Xbox One.

There was a slight delay between the CBS broadcast and the Twitter live-stream, but viewers largely complimented the high-definition quality of the game that appeared to stream for most without interruption. Football fans who otherwise wouldn’t have had access to the game gave a thumbs-up, and users who had forgotten they had Twitter accounts had a reason to come back.

Some users requested certain features, such as only showing tweets about the team they support in the accompanying Twitter feed. That feed, curated by the company, included tweets with the hashtag #TNF or those that mentioned one of the teams or players.

“It was exciting to see how the experience played out on Twitter with how fans reacted to the first [Thursday night] football live stream,” a Twitter spokesman said.

The positive reviews may help win over marketers who were on the fence about Twitter’s live-streaming ad pitch. Twitter, which paid $10 million for rights to the 10 Thursday night games this season, has been allotted about 15 local in-game ad spots for each. Advertisers such as Bank of America Corp. , Anheuser-Busch InBev NV and Ford Motor Co. have bought sponsorship packages, which were priced between $1 million to $8 million.

Initial reactions from some participating advertisers were promising.

“I think we’re feeling pretty good about it from a business standpoint. I know we’re feeling great about it from an experience standpoint,” said Lou Paskalis, senior vice president and enterprise media executive at Bank of America, adding that the Twitter live-stream could open up new ways for brands to interact with viewers during the game.

The 2.1 million viewers who at some point watched Thursday’s game on Twitter exceeded Mr. Paskalis’s expectation that the live-stream would draw at least 1.5 million total viewers. Twitter had informed him that Bank of America’s ads during the Thursday night game had a 98% completion rate. “That makes us really happy.”

“The free aspect is huge,” said Francois Lee, executive vice president and investment director at MDC & Partners media agency Assembly. By offering free streaming on the go and the ability to watch on the big screen through Apple TV and Amazon, Twitter is directly competing with networks such as CBS and Comcast Corp.’s NBC, he said.

At an investor conference Thursday, CBS Chief Executive Les Moonves said that before too long he expects to strike a deal with the NFL to stream games on its video-streaming site CBS All Access.

Others who work with advertisers were more cautious. “I feel as though it’s a nice compliment to the broadcast, but hardly a seismic change in how NFL is consumed,” said David Campanelli, senior vice president and director of video investment at media agency Horizon Media, which works with brands such as Geico insurance and Corona beer.

While Thursday night’s technological feat was a success, plenty of questions remain. Do viewers enjoy watching the game with running Twitter commentary alongside a smaller screen, or did they opt to minimize the social feed to watch the game full-screen? And after the initial buzz wears off, will this become a bona fide alternative to watching broadcasts that are available elsewhere?

“I think the Venn diagram of those who want to watch the NFL on a portion of a small phone screen while tweeting is pretty small,” RBC Capital analyst Mark Mahaney said in an email.

Thursday night football games last season averaged more than 17 million viewers on CBS and the NFL Network, according to Nielsen.

Write to Yoree Koh at yoree.koh@wsj.com and Alexandra Bruell at alexandra.bruell@wsj.com