The idolised forward feasted upon a vulnerable defence with glee in Brasilia on Monday, his first-half double sandwiching Joel Matip's unlikely leveller.
Brazil ultimately progressed with a degree of comfort, the much-maligned Fred and substitute Fernandinho adding further goals after the interval to secure a last-16 tie against fellow South Americans Chile.
Mexico were victorious against Croatia in Group A's other closing fixture, but failed to make up a goal-difference deficit as the hosts retained top spot.
While a routine triumph in which Brazil's star took his tournament tally to four goals will provide comfort, Luiz Felipe Scolari is unlikely to partake in too much backslapping.
Indeed, after coming through a group featuring no other major footballing powerhouse, Scolari is likely to demand more of his side as they prepare to face a Chile outfit that have impressed in the tournament to date.
It was Cameroon's susceptible backline that was first to be breached when Neymar, inexplicably unmarked, cleverly turned home Luiz Gustavo's low cross from the left.
Brazil's golden boy came agonisingly close to a second soon after, Charles Itandje producing a fine save to keep out his fizzing volley.
Despite their defence appearing increasingly hapless, Cameroon looked dangerous at the other end and fired a warning shot as Matip's header rattled the crossbar.
Not heeding the lesson proved costly for the hosts, too, as Matip side-footed Allan Nyom's cross into an empty net the next time he got an opportunity.
While those in front of him wilted in the face of pressure, Itandje was at least attempting to provide a steadying influence, getting down quickly to turn away Hulk's speculative hit.
But he could do little as another Brazilian, this time Fred, was left free in the area, the under-pressure forward heading home David Luiz's pass.
