This disclosure relates to intranasal administration of conjugates comprising guanidinylated aminoglycosides (“guanidinoglycosides”) and a polypeptide (e.g., an enzyme, antibody, or polypeptide growth factor). For example, such administration methods are useful for delivering a polypeptide to the brain and/or cerebrospinal fluid. Such methods are useful for treating a lysosomal storage disease through intranasal administration of a conjugate comprising one or more guanidinoglycosides and an enzyme useful for treating a lysosomal storage disease.