The first of three days of industrial unrest has led to school closures across the isles.
Workers are also poised to walk out tomorrow and on Thursday.
It comes after members of the public services union Unison voted to take industrial action in 26 council areas across Scotland, including Shetland.
The strike action affects members working in supporting roles, such as learning support workers, early learning and childcare staff, catering staff, janitors and office administrators.
The union’s branch branch chairwoman, Susanne Gens, said Cosla [Convention of Scottish Local Authorities] had shown “how little they value their own workforce”.
“The offer we received after two deadlines had passed, showed a small increase for the lowest paid staff, but there was no more or very little additional money on the table for the majority of our members.
“Our members are angry by the contempt the employer is showing.
“Our members are very aware of the disruption caused. Strike is always the last resort.
“Many have thought long and hard about taking action, but when you have members who worry about heating their home or feeding their families, there comes a point when members decide, that action needs to be taken.
“If it is a decision, between going cold and hungry or leaving the job you love, then it is time, the employer realises this.
“Members will be balloted to make it clear to Cosla and the Scottish government, that they will have to take LG staff seriously and show them the respect they deserve.”