The firm maintained its $15 price target on shares of the social media company, TheFly reports.
Although Twitter shares have been boosted by takeover speculation, Mizuho said the stock is overvalued at current levels.
Twitter's business fundamentals have "deteriorated significantly" over the past 12 months, and most of the potential buyers are unlikely to "play out," the firm added.
Of Twitter's potential suitors, Mizuho said it sees Alphabet's (GOOGL) Google and Salesforce.com (CRM) as the most likely options.
Additionally, Loop Capital downgraded Twitter to "sell" from "hold" and reiterated its $18 price target, according to TheFly.
The firm said any takeover offers are unlikely to offer a premium to the stock's current valuation.
Loop Capital added that the "swift manner" with which Twitter is approaching buyers insinuates that the company may be posting "another disappointing earnings report."
Separately, TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this articles's author. TheStreet Ratings has this to say about the recommendation:
TheStreet Ratings team rates Twitter as a Sell with a ratings score of D+. This is driven by multiple weaknesses, which it believes should have a greater impact than any strengths, and could make it more difficult for investors to achieve positive results compared to most of the stocks it covers. Among the areas the team feels are negative, one of the most important has been a generally disappointing historical performance in the stock itself.
You can view the full analysis from the report here: TWTR