A customs officer and another man have pleaded guilty to smuggling drugs into Australia by helping contraband pass through Sydney Airport undetected.

Paul John Katralis, 25, appeared in Central Local Court in Sydney on Wednesday and pleaded guilty to importing a commercial quantity of the precursor drug pseudoephedrine.

Court documents say he assisted others in the drug importation in March 2010.

He also pleaded guilty to receiving a bribe and abusing his office as a customs officer.

Sean Liam Hutchinson, 28, pleaded guilty to the same drug charge in the same court on Wednesday.

He helped import the same precursor drug some time between July and August 2012.

Both men have been committed for sentencing in Downing Centre District Court on January 18.

Two other men made their first appearances charged with the same drug import offence and had their matters adjourned until February 27.

Steven Vince Monaco, 22, and Alexander Riccio, 24, did not enter pleas when their matters were heard briefly in court on Wednesday.