For those having installed their helm client with snap, to downgrade/upgrade it to a specific version you can simply:

• Uninstall it: snap remove helm
• Check the available versions: snap info helm
• Install the one you want: snap install helm --channel=X.X/stable --classic

I experienced same issue, but in my case I wanna only to upgrade Tiller to specific version (because helm client is running remotely).

So, error was:

Error: UPGRADE FAILED: incompatible versions client[v2.11.0] server[v2.9.1]

Accordingly to documentation I've run:

$ kubectl --namespace=kube-system set image deployments/tiller-deploy tiller=gcr.io/kubernetes-helm/tiller:v2.11.0

deployment.extensions/tiller-deploy image updated

Documentation reference:

https://helm.sh/docs/install/#upgrading-tiller

Like the OP, I had this error:

$ helm list
Error: incompatible versions client[v2.10.0] server[v2.9.1]

Updating the server wasn't an option for me so I needed to brew install a previous version of the client. I hadn't previously installed client[v2.9.1] (or any previous client version) and thus couldn't just brew switch kubernetes-helm 2.9.1. I ended up having to follow the steps in this SO answer: https://stackoverflow.com/a/17757092/2356383

Which basically says

• Look on Github for the correct kubernetes-helm.rb file for the version you want (2.9.1 in my case): https://github.com/Homebrew/homebrew-core/search?q=kubernetes-helm&type=Commits
• Click the commit hash (78d6425 in my case)
• Click the "View" button to see the whole file
• Click the "Raw" button
• And copy the url: https://raw.githubusercontent.com/Homebrew/homebrew-core/78d64252f30a12b6f4b3ce29686ab5e262eea812/Formula/kubernetes-helm.rb

Now that I had the url for the correct kubernetes-helm.rb file, I ran the following:

$ brew unlink kubernetes-helm
$ brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/78d64252f30a12b6f4b3ce29686ab5e262eea812/Formula/kubernetes-helm.rb
$ brew switch kubernetes-helm 2.9.1

Hope this helps someone.

Another alternative, if changing the server version is not an option, is to use the helm installer script

The script lets you chose a specific version like so ./get_helm.sh -v v2.13.1

Another approach to using different versions through Docker.

https://hub.docker.com/r/alpine/helm

Example: list helm packages installed

docker run -it --rm \
    -v ~/.kube/config:/root/.kube/config \
    -v ~/.helm:/root/.helm alpine/helm:2.9.1 \
    list

This is a long command; but it can be shortened with an alias

alias helm_2_9_1="docker run -ti --rm \
    -v $(pwd):/apps -v ~/.kube/config:/root/.kube/config \
    -v ~/.helm:/root/.helm alpine/helm:2.9.1"

And then the command is

helm_2_9_1 list

This answer is for who want to choose(downgrade) helm client version, and the brew install is not work.You can just manually install the binary file from here.

example:

1. you can unlink the current helm

   brew unlink kubernetes-helm

2. choose and download the helm version you want in github helm------v2.8.2

3. unzip the file and put the helm unix executable binary file into /usr/local/bin directory

   go to the directory you just downloaded

   cd /Users/your_name/Downloads

   unzip the file

   gunzip -c helm-v2.8.2-darwin-amd64.tar.gz | tar xopf -

   copy to the bin directory

   cp darwin-amd64/helm /usr/local/bin

4. now you will see the right version of helm you want

   helm version

This probably isn't the most advanced answer... but my team runs kubernetes clusters that already have tiller installed. While setting up a new laptop, I wanted my helm to match the tiller version, so I found it like this:

TILLER_POD=`kubectl get pods -n kube-system | grep tiller | awk '{print $1}'`
kubectl exec -n kube-system $TILLER_POD -- /tiller -version

Then I just used the normal helm install instructions from that release number (being on Linux, its basically just curl and unzip to /usr/local/bin).