The five-floor shop sits on Madrid's iconic Gran Vía and is the biggest Primark in mainland Europe. For several weeks after its opening, customers had to queue to get in, demand for the brand's cheap and cheerful clothing was so high.
But the huge crowds have also drawn huge numbers of thieves, who have been stealing from the store itself as well as pickpocketing its customers.
The problem has become so bad that police in Madrid have asked Primark to employ extra security staff to tackle the issue.
Police have already broken up four pickpoceting gangs, Madrid's head of police Alfonso José Fernández said during a police display in Madrid's Las Ventas, adding that there had been a "wave of thefts" and police were "overwhelmed".
He said that there had been over 300 reports of theft made to the police station in nearby Calle Leganitos - the closest to the store - every month since Primark opened in October 2015.
Fernández confirmed he had asked Primark to reinforce its security by employing extra staff, adding that he had put extra officers on the beat in the area and dismantled four criminal gangs operating within the store.
Primark overtook Spanish brand Zara to become Spain's most popular fashion store in terms of number of customers in 2015.
In 2015 alone 8.9 million customers made purchases in Primark stores in Spain, beating Zara's 8.2 million customers.