It depends what you mean by the question. If the question is do Mormons worship more than one God, the answer is a definitive “no”. If the question is do Mormons believe more than one god exists, the answer is “yes”.
If Mormons believe that multiple gods exist, but they only worship one of them as God, does that mean Mormons are polytheists or that Mormonism is a form of polytheism?
Mormonism is certainly not polytheistic in the way the Hindu religion is. Mormons do not believe there is any being that can do anything for them other than God. Each individual Hindu might worship one god, but they believe they can change their allegiance to another god if they so desire (at least this is my understand of Hinduism, which is admittedly very limited). I know a bit more about the Greek gods such as Zeus, so perhaps it’s better to use them as an example. In ancient Greek society one might worship Zeus but then switch to Apollo or Hera, believing that each god could grant them favors. Mormons do not believe any such thing. Mormons believe there is only one God they can worship, and that no other god can do anything for them.
Dictionary.com merely defines polytheism as “the doctrine of or belief in more than one god or in many gods.” Unfortunately, this definition does not define what is meant by “belief”. Belief in this context can mean “worship” or “belief in the existence of”.
TheFreeDictionary.com has a better definition that defines polytheism as “The worship of or belief in more than one god.” Mormons certainly don’t worship more than one God, so if we assume that this definition is using “belief” as a synonym for worship then according to this definition Mormons are not polytheists.
An appeal to an encyclopedic definition of polytheism is probably most helpful. What is described on that webpage is in stark contrast to Mormon beliefs.
Are there passages in the Bible that lead one to believe there is only one God, and no other can exist? Sure, but it depends on your interpretation and assumptions. But as long as we’re in the business of discussing such things, feel free to post all your opinions, thoughts, interpretations, and assumptions and let’s discuss them. As usual, I don’t expect anyone will convince the other, but I always welcome to opportunity to reach greater understanding over each others’ viewpoints.