An adjustable dumbbell device includes a handle bar having a bore formed in the handle bar, and having a slot formed in one end of the handle bar, a weight member includes an engaging member for engaging with the slot of the handle bar and for detachably attaching to the handle bar, the weight member includes an orifice for aligning with the bore of the handle bar, and a latch is slidably engaged into the bore of the handle bar, and extendible out of the handle bar and engageable into the orifice of the weight member for securing the weight member to the handle bar. One or more weight members are adjustably attached to the handle bar.