The resource rose 82% to 29.97 million tonnes at 4.7% lead equivalent and 0.6% zinc, while indicated resources jumped 123% to 10.85Mt at 5% lead equivalent and 0.4% zinc.
The estimate was completed by CSA Global, incorporating drilling from late 2018.
Initial results from a mining study supported the lowering of the cut-off grade from 2.5% lead to 1% lead.
A review of preliminary dense media separation test work has indicated ore could be upgraded by 2-3 times prior to processing.
The resource and metallurgical results will feed into a review of the 2012 prefeasibility study and update, due for release later this month.
"As data continues to come in from final drill holes completed in late 2018 and with phase two drilling planned to commence in April, these resource figures are expected to rise further in 2019," Pacifico managing director Simon Noon said.
"We are confident that the Sorby Hills resource base will continue to grow and subject to successful development the project could potentially become one of Australia's most significant lead producers."
Pacifico is aiming for a further resource upgrade in the September quarter to support an optimised PFS.
The company acquired a 75% stake in Sorby Hills last year.
Pacifico shares were unchanged at half a cent, valuing the company at $8.2 million.