The dress code for 'worship' will depend on the customs of local people. Jehovah's Witnesses do not want to 'stumble' someone or put the organization in a negative light by wearing clothing that is inappropriate. Neat grooming and good personal hygiene is also expected.
Therefore their dress code for formal, public events is business to dressy attire.
Women cannot wear pants because men are expected to be masculine and women are expected to be feminine.
Men wear dress pants to Kingdom Halls. Women wear skirts or dresses. See Equality
In the USA, Canada, and other countries, inappropriate clothing for Kingdom Hall meetings, conventions, book studies, preaching activities, and all formal gatherings typically includes:
'Overly casual' clothing is considered inappropriate.
Also inappropriate for both sexes is rebellious or 'worldly' clothing. This would include provocative, sexually arousing clothing, tight clothes or pants, apparel with sexual, evil, or rebellious images, T-Shirts with 'inappropriate images or words that are contrary to the high moral standards and beliefs of the Watchtower religion.
For women, very short skirts and dresses are not appropriate. Neither are tops with low cut necklines.
Clothing for men and women is expected to be neat, clean, and modest.
Males typically wear suits, dress shirts, dressy shoes, and ties. Women wear dresses or skirts.
Jehovah's Witnesses cannot wear blue jeans, sweats, shorts, running shoes, etc to Kingdom Halls for worship. They can wear those things of course if they're not there for worship. e.g. they might be there to clean, fix, paint, do clerical work, meet friends, etc.
The Watchtower says, 'Overly casual attire is immodest and inappropriate for worship. Worn-out book bags and dog-eared or soiled Bibles also detract from the Kingdom message.' Watchtower Nov 1, 1987, 'Are You Remaining Clean in Every Respect?', par 6.
When JW's are not worshiping Jehovah, i.e. going to meetings or out in preaching activities, they can wear almost anything as long as the clothing is 'modest' and in harmony with Watchtower teachings.
As mentioned above they can't wear provocative, sexually revealing clothing or items that would indicate they do not support all the beliefs of Jehovah's Witnesses.
Jehovah's Witnesses must not own a cross. Therefore they wouldn't wear a cross or wear clothing with an image of a cross on it.
They wouldn't wear Halloween or Christmas clothing because those are some of the holidays JW's don't celebrate.
They wouldn't wear clothing depicting political ideals because JW's are politically neutral. See Flag
They wouldn't wear clothing promoting tobacco products because JW's are not allowed to smoke.
JW's can't wear military apparel because they don't go to war.
Continued: > 141 Things Jehovah's Witnesses Can't Do