The phrase "uncertain of whether" is grammatically correct and is commonly used in written English.
It is typically used when someone is unsure or hesitant about something and wants to express their uncertainty. Example: I am uncertain of whether I should apply for the job or not.
Hamilton "felt uncertain of whether he was going to be accepted in spite of his talents," Mr. Fleming said.
Lee was "surprised and delighted" by the find, said the statement, but uncertain of whether the draft deserved publication.
Often she seemed uncertain of whether or not to untether herself from her seat and work the stage.
In the face of everybody else's debate, we're being forced into ambivalence, uncertain of whether we're overachievers, underachievers or even achieving anything at all.
After getting one picture, the machine broke, leaving both pitcher and doctors uncertain of whether the injury was a contusion that the first picture indicated, or something worse.
Moore's book, psychologically deep yet racheting up foreboding like a thriller, puzzled reviewers, who were uncertain of whether to classify it as literary or genre fiction.
"It's got to the stage where players are uncertain of their payments, whether it's appearance money or bonuses.
Despite being faced with an uncertain future of whether the diminishing land they live on will stay above the rising tide, the tribes still persist and continue to adapt to a changing environment and a transforming subsistence-based livelihood.
We need more.' " President Bush had said that there are 60 lines of cells available for research, but some scientists said they were uncertain of that number, or whether it was sufficient.
It is, of course, uncertain whether all of them are actually negative.
The vanilla crop was also severely affected, and the mayor of Mananara was uncertain whether any of the crop could be harvested.
