Even if you think the way you were let go was unfair or terrible, don’t badmouth your former employer or boss in an interview. This makes you look negative and often changes the way the interviewer sees you. If the interviewer asks you to elaborate about your boss or former company, you can say something like, "The company just wasn't a good fit for me, because it didn't present the types of challenges I most enjoy." Or you can say, "My boss is great at his job, but our personalities just didn't fit well." ” Don’t lie, but you don’t have to be obvious about it either. Instead, you can say things like “my company downsized” or “my position was eliminated.” If it’s apparent to the interviewer that you were fired for a more specific reason that downsizing, explain what happened in as few words as possible. For example, you can say something like “I learned that I should really research the companies I apply to, to make sure that their goals and mine match. For example, I noticed that your company’s commitment to social justice matches my own passion for it, which is exemplified by my work with the ACLU.” Interviewers will tend to have more respect for you if you take responsibility for being fired. This doesn’t necessarily mean accepting blame if you weren’t at fault, but it can mean acknowledging the position wasn’t a good fit or you didn’t get along with your bosses or coworkers. For example, you can say something like “You can see on my resume that being involuntarily let go from a position is not commonplace for me. The truth is that my boss and I did not get along well and the position wasn’t a good fit. I’ve learned a lot from the position, and my references will attest to my excellence as an employee and coworker.”

Summary:
Don’t talk about your previous boss or company. Avoid saying “fired. Be concise, then move on. Take responsibility.