In Salesforce Lightning Experience, when a Case is related to a Contact, via the standard 'Contact Name' field, the 'Account Name' is automatically populated when it has no value. However, when a User has Edit access to the 'Case: Account Name' field, any subsequent changes to the related Contact will not automatically change the related Account. The related Account would need to be manually changed instead.
Note: The workaround provided below is only intended for use in the Lightning Experience. Users with read-only access to the 'Account' field will still find that the 'Account' field is automatically updated when the 'Case Contact' field is updated in the Classic UI.
Alternatively, you could set up the process on the Case object as described below to automatically populate Account associated with the Contact under 'Account Name' field on the Case record:
[Case].ContactId(Field) IsNull (operator) Boolean (Type) False (Type) [Case].ContactId(Field) Ischanged(operator) Boolean (Type) True (Type)
Account ID (Field) Reference (Type) [Case].Contact.AccountId (Value)
000387888

We use three kinds of cookies on our websites: required, functional, and advertising. You can choose whether functional and advertising cookies apply. Click on the different cookie categories to find out more about each category and to change the default settings.
Privacy Statement
Required cookies are necessary for basic website functionality. Some examples include: session cookies needed to transmit the website, authentication cookies, and security cookies.
Functional cookies enhance functions, performance, and services on the website. Some examples include: cookies used to analyze site traffic, cookies used for market research, and cookies used to display advertising that is not directed to a particular individual.
Advertising cookies track activity across websites in order to understand a viewer’s interests, and direct them specific marketing. Some examples include: cookies used for remarketing, or interest-based advertising.