In her first earnings call since she joined the business in July, Mayer said that Yahoo "hasn’t capitalised" on the mobile opportunity.
She said: "We haven't effectively optimized our websites, we've underinvested in our mobile front-end development and we've splintered our brands. All of this needs to change."
Meyer said the business's top priority was a "focused and coherent mobile strategy". She said Yahoo was well positioned in mobile because of its content verticals, such as finance and sport, which consumers wanted to access on their smartphone devices.
Her words echo those of Silicon Valley rivals Facebook and Google, which have both homed in on the importance of mobile for future growth.
While Yahoo's results have regularly disappointed Wall Street expectations in recent years, this quarter it beat them.
Net income climbed to $3.16bn (£1.97m), for the quarter ended 30 September, from $298.3m (£186.6m) for the same period last year.
Revenue growth, excluding traffic acquisition costs paid to partners, rose to $1.09bn (£682m) from $1.07bn (£667m) in the same period last year.
Yahoo did not break out UK revenues, but EMEA revenues suffered, dropping 18% year on year to reach $79m (£49m).
Display revenue, excluding traffic acquisition costs (TAC), was flat at $452m (£283m), compared to $449m (£281m) for the same period last year. Search revenue excluding TAC grew 10% year on year to reach $414m (£259m).
Operating costs, which hit Yahoo's results last quarter, were down 4.8% to reach $369m (£281m).
Yahoo has seen a revolving door of new appointments and departures in recent months. On the call, Mayer said she now had her "dream team" in place.
Her turnaround strategy for the business has been eagerly awaited. She said: "We're committed to going back to our roots as a consumer internet company".