How important is body language for interviews?

It is as important as half the interview!

It's not very important.  The reality is that the first few seconds of an interview are by far the most important part, and of that the first few tenths of a second are by far the most important part.   In other words by the time you start to shake hands with the interviewer you are more than half way through, so what books on body language you have read to improve your handshake don't matter very much.

Naturally talented interviewers, or those who have properly studied how to interview and are sufficiently reflective to make good use of their training, do not suffer from this problem.  However such people are a) rare and b) likely to spot and dislike 'learnt' body language behaviours.

In other words, just do what your parents or guardians [probably] told you when you were little.  Stand up straight, look people in the eye and smile, say please and thank you, and remember that if you are in an interview you have been selected to be there and you are therefore entitled to a fair crack at the job.

Before you get into the mind, you have to inhabit the physicality. Body language is a great way of speaking - a very powerful tool. We had body language before we had speech, and apparently, 80% of what you understand in a conversation is read through the body, not the words. 

In an interview - your image is your brand and you have only one opportunity to make that first impression using everything you have got including your speech and your body. A great attitude towards your interview approach is demonstrated by the confidence of your body. For instance - a poor posture shows uncertainty and a lack of confidence and ability. Contrarily, a good posture conveys confidence and an air of capability. It does not take the striking pose of a high-fashion model or the strict stance of someone in uniform to earn respect and admiration in an interview. Think of good body language as your body’s projection of a positive message to those you meet - including your interviewer.

Body language is important as long as it doesn't over shadow the real purpose of the interview.

Body language is as critical as verbal communication  in an interview.

Body language is related to eye contact , gestures , posture , body coordination.  

Your sitting posture defines , how an interview will go , Will it be positive or negative.

Your body should support your words otherwise , words become irrelevant.

Actually body language plays a bigger role in any communication.

As words have power, body language also has power not only in interviews but all times.

Those who can use language powerfully and explicitly have better opportunity to deliver the message they want to be understood, the same happens with body language.

If I want to build rapport early at the the interview this can be done using body language, if I wanted to show confidence, understanding, agreeing, disagreeing and even opposition all these can be done using the proper body language which is not necessarily to be fake or fabricated. What comes out the heart touches the heart and what comes out the tongue hardly crosses the ears.

The role of body language in interviews is underestimated and under utilised.

With body language you can use your hands and face to communicate properly with visual, auditory and kinaethetic type personality of interviewers, this can not be done with only one style of spoken language.           

Thanks for the invitation, this have been a debated point in psychology for ages & still remains to be so.

It's very important, contributes 55% about the candidate. However it also may lead to false positive, to avoid that reliability must be established along with this. 

Darwin had proved that expressions are inherited, are different among various cultures & finally the environment in which one has grown up.

So, the key of this is in how it's being interpreted, the culture background of all (assessor, assessee & for it's being assessed) and under what circumstances. 

Thanks to invite.

Your physical appearance is the first tact to develop a good image for interviewer with your realistic body language. Expression of professionalism with balanced body language is the key to success. 

Thank you for the invitation and I agree with you my teacher Aziz

Repeated question. body language shows whats inside you. so it can have positive and negative effects.

Thanks for invitation,

Totally agree with Mr. Ali Ahmad in his valuable answer.