The dispute relates to a row over contracts for some staff
Tesco say all its stores will remain open on Wednesday, as strike action continues across a number of stores.
The strike got underway earlier today at eight stores across the country.
Members of the Mandate union are taking the 'indefinite' action over changes to the employment contracts of over 250 longest-serving workers.
The union say this is being done without agreement, and the new contracts include cuts to pay and conditions at work.
Tesco, meanwhile, has argued that the terms of the contracts mean they have too many people working during the earlier, quieter times of the week.
The eight Tesco stores impacted by the action are:
Workers from another eight stores are due to strike from Friday February 17th:
Mandate has thanked the public for their "strong show of support" for striking workers during the first day of action.
The union's General Secretary John Douglas said: "Given the support the striking workers have received all day, the public clearly recognise the importance of the issues involved here – namely that Tesco Ireland, which has enormous economic power, is attempting to unilaterally impose changes to the contracts of employment for approximately 250 workers.
“If Tesco Ireland is successful with this move it would result in some workers experiencing reduced incomes of up to 20%. The company – which is the most profitable retailer in the country with estimated profits of more than €250 million annually – has never justified the cuts they are seeking to impose on workers who earn slightly more than €14 per hour," he added.
In a statement, Tesco said: "Like colleagues, we have been shocked at Mandate’s moves on two levels, firstly to refuse to abide by the Labour Court which is the cornerstone of the industrial relations system in Ireland and secondly by advocating that customers shop in non-union competitor supermarkets.
"Mandate’s action is a retrograde step for the industrial relations processes of the State which it undermines. The Labour Court Recommendation is the only solution to this dispute. We would like to assure everyone that we have done everything we can to resolve this issue fairly for all involved."
Meanwhile, balloting for industrial action is to take place in a further 23 stores next week.