This study investigated how aging modulates semantic encoding. We used a task where participants were required to determine the semantic relatedness between the cue and target stimuli. Single-character Chinese words were the cues, whereas two-character words describing the cues were the targets. The targets can be visual-based (appearance) or associative-based (meaning). Experiment One compared the reaction times on the two types of targets between older (n = 29) and younger participants (n = 31). Older participants performed significantly slower on the visual- than associative-based trials, while the younger participants showed no difference. The results suggest that aging would hinder semantic encoding of visual- rather than associative-based processes. The slowness in processing is likely attributable to age-related decline in attentional control. Experiment Two tested the aging effect on top-down attentional control by presenting pre-cue before each trial on older (n = 26) and younger participants (n = 49). The results indicated that valid pre-cue reduced the latency differences between the visual- and associative-based trials among the older participants. The valid pre-cues were found to effectively shorten the reaction time of the visual-based trials suggesting possible facilitation of attentional control among the older adults. Our findings substantiate age-related attentional control decline only in visual- but not associative-based processing. Future studies should explore the mechanisms underlying such differential age-related effect. Copyright © 2017 Wiley Periodicals, Inc.